diff --git a/.github/workflows/cygwin-bootstrap.yml b/.github/workflows/cygwin-bootstrap.yml
new file mode 100644
index 0000000000000..d0e4ec1a71bfd
--- /dev/null
+++ b/.github/workflows/cygwin-bootstrap.yml
@@ -0,0 +1,31 @@
+name: Cygwin Bootstrap Release
+on:
+  push:
+    tags: 'bootstrap/*'
+
+permissions:
+  contents: write
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Create Release
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+        run: |
+          tag="${GITHUB_REF_NAME}"
+          gh release create --draft "$tag" --title "$tag"
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: DeterminateSystems/nix-installer-action@c5a866b6ab867e88becbed4467b93592bce69f8a
+      - uses: DeterminateSystems/magic-nix-cache-action@b4ad0b1e587499958543d6e793cd46510a21e7c2
+      - name: Build
+        run: nix build -f pkgs/top-level/release-cross.nix bootstrapTools.x86_64-pc-cygwin.unpack -o unpack.nar.xz
+      - name: Upload
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+        run: gh release upload "${GITHUB_REF_NAME}" unpack.nar.xz
diff --git a/.github/workflows/cygwin.yml b/.github/workflows/cygwin.yml
new file mode 100644
index 0000000000000..a9ae42de60c8d
--- /dev/null
+++ b/.github/workflows/cygwin.yml
@@ -0,0 +1,55 @@
+name: cygwin
+
+permissions: {}
+
+on:
+  push:
+
+jobs:
+  build-tarball:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: DeterminateSystems/nix-installer-action@c5a866b6ab867e88becbed4467b93592bce69f8a
+      - uses: DeterminateSystems/magic-nix-cache-action@b4ad0b1e587499958543d6e793cd46510a21e7c2
+      - name: build tarball
+        run: nix build -f nixos/release.nix cygwinTarball.x86_64-linux
+      - uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
+        with:
+          name: tarball
+          path: result
+  build-bootstrap:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: DeterminateSystems/nix-installer-action@c5a866b6ab867e88becbed4467b93592bce69f8a
+      - uses: DeterminateSystems/magic-nix-cache-action@b4ad0b1e587499958543d6e793cd46510a21e7c2
+      - name: build bootstrap
+        run: nix build -f pkgs/top-level/release-cross.nix bootstrapTools.x86_64-pc-cygwin.unpack -o unpack.nar.xz
+      - uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
+        with:
+          name: bootstrap
+          path: unpack.nar.xz
+  test:
+    runs-on: windows-latest
+    needs: build-tarball
+    steps:
+      - uses: actions/download-artifact@37930b1c2abaa49bbe596cd826c3c89aef350131 # v7.0.0
+        with:
+          name: tarball
+      - name: install
+        run: tarball/install.ps1 cygwin
+      - name: get-info
+        shell: pwsh cygwin/cygwin.ps1 {0}
+        run: nix-info
+    # - name: build
+    #   shell: pwsh cygwin/cygwin.ps1 {0}
+    #   run: nix build --no-sandbox nixpkgs#hello
+    # - uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
+    #   with:
+    #     name: tarball
+    #     path: result
diff --git a/bootstrap.nix b/bootstrap.nix
new file mode 100644
index 0000000000000..1b8e999df6f13
--- /dev/null
+++ b/bootstrap.nix
@@ -0,0 +1 @@
+/nix/store/2m6hgrgdccz1yrpqlda0iz3ysxcipnj2-unpacked
diff --git a/check-cygwin b/check-cygwin
new file mode 100755
index 0000000000000..818e0f5175c21
--- /dev/null
+++ b/check-cygwin
@@ -0,0 +1,14 @@
+#!/bin/sh
+set -eo pipefail
+echo BAD:
+nix derivation show -r .#cygwinSystem.config.system.build.tarball.stdenvDeps \
+    | jq -r 'map_values(select(.system == "x86_64-cygwin")) | keys_unsorted .[]'
+
+nix derivation show -r -f. --argstr system x86_64-cygwin nix \
+    | jq -r 'map_values(select(.system == "x86_64-linux")) | keys_unsorted .[]' \
+    | sort > target
+nix derivation show -r .#cygwinSystem.config.system.build.tarball.stdenvDeps \
+    | jq -r 'map_values(select(.system == "x86_64-linux")) | keys_unsorted .[]' \
+    | sort > bootstrap
+echo MISSING:
+comm -13 bootstrap target
diff --git a/cygwin-custom.nix b/cygwin-custom.nix
new file mode 100644
index 0000000000000..47a5db76930eb
--- /dev/null
+++ b/cygwin-custom.nix
@@ -0,0 +1,20 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+
+{
+  imports = [
+    ./cygwin-system.nix
+  ];
+
+  environment.systemPackages = [ pkgs.rsync ];
+
+  nix = {
+    extraOptions = ''
+      secret-key-files = /var/store-key
+    '';
+  };
+}
diff --git a/cygwin-system.nix b/cygwin-system.nix
new file mode 100644
index 0000000000000..4af7563b023de
--- /dev/null
+++ b/cygwin-system.nix
@@ -0,0 +1,23 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+
+{
+  imports = [
+    ./nixos/maintainers/scripts/cygwin/system.nix
+    ./nixos/maintainers/scripts/cygwin/tarball.nix
+  ];
+
+  nix = {
+    settings.experimental-features = [
+      "nix-command"
+      "flakes"
+    ];
+  };
+
+  nixpkgs.buildPlatform = lib.mkDefault builtins.currentSystem;
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-cygwin";
+}
diff --git a/hydra/flake.lock b/hydra/flake.lock
new file mode 100644
index 0000000000000..b1c86ff778843
--- /dev/null
+++ b/hydra/flake.lock
@@ -0,0 +1,25 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1764587062,
+        "narHash": "sha256-hdFa0TAVQAQLDF31cEW3enWmBP+b592OvHs6WVe3D8k=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "c1cb7d097cb250f6e1904aacd5f2ba5ffd8a49ce",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/hydra/flake.nix b/hydra/flake.nix
new file mode 100644
index 0000000000000..1327ee59199c1
--- /dev/null
+++ b/hydra/flake.nix
@@ -0,0 +1,49 @@
+{
+  outputs =
+    { nixpkgs, ... }:
+    {
+      nixosConfigurations.container = nixpkgs.lib.nixosSystem {
+        system = "x86_64-linux";
+        modules = [
+          {
+            boot.isNspawnContainer = true;
+
+            services.hydra = {
+              enable = true;
+              hydraURL = "http://localhost:3000";
+              notificationSender = "hydra@localhost";
+              useSubstitutes = true;
+            };
+
+            networking.firewall.allowedTCPPorts = [ 3000 ];
+            networking.useHostResolvConf = nixpkgs.lib.mkForce false;
+            networking.nameservers = [ "8.8.8.8" ];
+
+            programs.ssh.extraConfig = nixpkgs.lib.mkAfter ''
+              Host cygwin-vm
+                User Quickemu
+                HostName 10.233.1.1
+                Port = 22220
+            '';
+
+            services.openssh = {
+              knownHosts = {
+                cygwin-vm = {
+                  hostNames = [ "[10.233.1.1]:22220" ];
+                  publicKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHJGc5UkkNeYGjBLpgvdZZ8GeW8QtZsvC9IuTMNzLJ/N";
+                };
+              };
+            };
+
+            nix.distributedBuilds = true;
+            nix.buildMachines = [
+              {
+                hostName = "cygwin-vm";
+                system = "x86_64-cygwin";
+              }
+            ];
+          }
+        ];
+      };
+    };
+}
diff --git a/lib/systems/flake-systems.nix b/lib/systems/flake-systems.nix
index 851dc1af71818..050551bff594f 100644
--- a/lib/systems/flake-systems.nix
+++ b/lib/systems/flake-systems.nix
@@ -25,4 +25,5 @@
   "powerpc64le-linux"
   "riscv64-linux"
   "x86_64-freebsd"
+  "x86_64-cygwin"
 ]
diff --git a/maintainers/scripts/bootstrap-files/refresh-tarballs.bash b/maintainers/scripts/bootstrap-files/refresh-tarballs.bash
index 0fa2c28bb18a4..e50b0f01d10ce 100755
--- a/maintainers/scripts/bootstrap-files/refresh-tarballs.bash
+++ b/maintainers/scripts/bootstrap-files/refresh-tarballs.bash
@@ -99,6 +99,7 @@ CROSS_TARGETS=(
     s390x-unknown-linux-gnu
     x86_64-unknown-freebsd
     loongarch64-unknown-linux-gnu
+    x86_64-pc-cygwin
 )
 
 is_cross() {
@@ -168,6 +169,7 @@ for target in "${targets[@]}"; do
         *linux*) nixpkgs_prefix="pkgs/stdenv/linux" ;;
         *darwin*) nixpkgs_prefix="pkgs/stdenv/darwin" ;;
         *freebsd*) nixpkgs_prefix="pkgs/stdenv/freebsd" ;;
+        *cygwin*) nixpkgs_prefix="pkgs/stdenv/cygwin" ;;
         *) die "don't know where to put '$target'" ;;
     esac
 
diff --git a/nixos/maintainers/scripts/cygwin/profile.nix b/nixos/maintainers/scripts/cygwin/profile.nix
new file mode 100644
index 0000000000000..2ccc1be8bec6a
--- /dev/null
+++ b/nixos/maintainers/scripts/cygwin/profile.nix
@@ -0,0 +1,94 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+
+{
+  imports = [
+    ../../../modules/profiles/minimal.nix
+  ];
+
+  config = lib.mkIf pkgs.stdenv.hostPlatform.isCygwin {
+    boot = {
+      bcache.enable = false;
+      initrd = {
+        supportedFilesystems = [ ];
+      };
+      kernel.sysctl = lib.mkForce { };
+      loader.grub.enable = false;
+      modprobeConfig.enable = false;
+      supportedFilesystems = [ ];
+    };
+
+    console.enable = false;
+
+    fonts.fontconfig.enable = false;
+
+    # the default requires glibcLocales
+    i18n.supportedLocales = [ ];
+
+    networking = {
+      dhcpcd.enable = false;
+      firewall.enable = false;
+      resolvconf.enable = false;
+    };
+
+    programs = {
+      fuse.enable = false;
+      less.enable = lib.mkForce false;
+      nano.enable = false;
+      ssh.systemd-ssh-proxy.enable = false;
+    };
+
+    security = {
+      pam.enable = false;
+      shadow.enable = false;
+      sudo.enable = false;
+    };
+
+    services = {
+      lvm.enable = false;
+      udev.enable = false;
+    };
+
+    system = {
+      disableInstallerTools = true;
+      # this is needed because tasks/filesystems.nix unconditionally adds
+      # dosfstools, and tasks/filesystems/ext adds e2fsprogs
+      fsPackages = lib.mkForce [ ];
+      # these match the cygwin defaults when "file" is prepended
+      nssDatabases = {
+        passwd = [ "db" ];
+        group = [ "db" ];
+      };
+    };
+
+    systemd = {
+      enable = false;
+      coredump.enable = false;
+    };
+
+    users = {
+      users = lib.mkForce { };
+      groups = lib.mkForce { };
+    };
+
+    environment.corePackages =
+      with pkgs;
+      lib.mkForce [
+        bash
+        coreutils
+        openssh
+        curl
+        config.nix.package
+      ];
+    environment.defaultPackages = lib.mkForce [ ];
+
+    nix = {
+      settings.sandbox = false;
+      package = pkgs.nixVersions.git;
+    };
+  };
+}
diff --git a/nixos/maintainers/scripts/cygwin/system.nix b/nixos/maintainers/scripts/cygwin/system.nix
new file mode 100644
index 0000000000000..56027a7678959
--- /dev/null
+++ b/nixos/maintainers/scripts/cygwin/system.nix
@@ -0,0 +1,76 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+
+let
+  inherit (pkgs)
+    bash
+    buildEnv
+    coreutils
+    runCommand
+    writeShellScript
+    cygwin
+    ;
+
+  nix = config.nix.package;
+
+  sw = buildEnv {
+    name = "cygwin-root";
+
+    paths = config.environment.systemPackages;
+
+    nativeBuildInputs = [
+      ../../../../pkgs/build-support/setup-hooks/make-symlinks-relative.sh
+    ];
+  };
+
+  activate = writeShellScript "activate" ''
+    (
+      export PATH=${
+        lib.makeBinPath [
+          coreutils
+          nix
+        ]
+      }:/bin
+      mkdir -p /nix/var/nix/gcroots
+      ln -sfn /run/current-system /nix/var/nix/gcroots/current-system
+      mkdir -p /run
+      ln -sfn '${lib.getExe bash}' /bin/sh
+      ln -sfn '@out@' /run/current-system
+      ln -sfn /run/current-system/etc /etc
+      if [[ -f /nix-path-registration ]]; then
+        nix-store --load-db < /nix-path-registration
+        rm -f /nix-path-registration
+      fi
+    )
+  '';
+
+  cygwin1 = cygwin.newlib-cygwin.out + "/bin/cygwin1.dll";
+
+in
+{
+  options = {
+    system.cygwin.toplevel = lib.mkOption {
+      type = lib.types.package;
+      readOnly = true;
+    };
+  };
+
+  imports = [
+    ./profile.nix
+  ];
+
+  config = {
+    system.cygwin.toplevel = runCommand "cygwin-system" { } ''
+      mkdir "$out"
+      ln -sr "${sw}" "$out"/sw
+      ln -sr "${cygwin1}" "$out"/
+      cp "${activate}" "$out"/activate
+      substituteInPlace $out/activate --subst-var-by out "$out"
+      ln -sr "${config.system.build.etc}"/etc $out/etc
+    '';
+  };
+}
diff --git a/nixos/maintainers/scripts/cygwin/tarball.nix b/nixos/maintainers/scripts/cygwin/tarball.nix
new file mode 100644
index 0000000000000..3f05487b18d77
--- /dev/null
+++ b/nixos/maintainers/scripts/cygwin/tarball.nix
@@ -0,0 +1,146 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+
+let
+  inherit (pkgs)
+    bash
+    buildPackages
+    cygwin
+    gnutar
+    lib
+    runCommand
+    writeShellScript
+    writeText
+    ;
+
+  nix = config.nix.package;
+
+  bootScript = writeText "cygwin.ps1" (
+    lib.replaceString "\n" "\r\n" ''
+      $ErrorActionPreference = 'Stop'
+      cp $PSScriptRoot\nix\var\nix\profiles\system\cygwin1.dll $PSScriptRoot\bin\cygwin1.dll
+      $bash = "$PSScriptRoot${lib.replaceString "/" "\\" (lib.getBin bash).outPath}\bin\bash.exe"
+      & $bash /nix/var/nix/profiles/system/activate
+      if (!$?) { throw 'activation script failed' }
+      & $bash --login -i $args
+      if (!$?) { exit 1 }
+    ''
+  );
+
+  cygwin1 = cygwin.newlib-cygwin.out + "/bin/cygwin1.dll";
+
+in
+{
+  options.system.cygwin.tarball = lib.mkOption {
+    type = lib.types.package;
+    readOnly = true;
+  };
+
+  config = {
+    environment.etc."profile".text = ''
+      export CYGWIN=winsymlinks=native\ $CYGWIN
+    '';
+
+    system.cygwin = {
+
+      tarball =
+        let
+          install = writeText "install.ps1" (
+            lib.replaceString "\n" "\r\n" ''
+              param ([Parameter(Mandatory=$true)][string]$dir)
+
+              $ErrorActionPreference = 'Stop'
+
+              $_ = mkdir -force $dir
+
+              fsutil file setCaseSensitiveInfo $dir enable
+              if (!$?) { throw 'setCaseSensitiveInfo failed, this may require: Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Windows-Subsystem-Linux' }
+
+              $_ = ni $dir\.test-target
+              try {
+                cmd /c mklink $dir\.test-link $dir\.test-target
+                if (!$?) {
+                  throw 'failed to create symbolic link: developer mode may need to be enabled'
+                }
+              } catch {
+                throw
+              } finally {
+                rm $dir\.test-target
+              }
+              rm $dir\.test-link
+
+              $env:CYGWIN = "winsymlinks=native"
+              # create cygwin1.dll so that symlinks to it are created properly
+              if(!(Test-Path $dir\bin\cygwin1.dll))
+              {
+                mkdir -f $dir\bin
+                ni $dir\bin\cygwin1.dll
+              }
+              & $PSScriptRoot\tar -C $dir --force-local -xpf $PSScriptRoot\${config.system.cygwin.tarball.fileName}.tar${config.system.cygwin.tarball.extension}
+              if (!$?) { throw 'failed to extract tarball' }
+            ''
+          );
+
+          system = config.system.cygwin.toplevel;
+        in
+        (pkgs.callPackage ../../../lib/make-system-tarball.nix {
+          # HACK: disable compression
+          compressCommand = "cat";
+          compressionExtension = "";
+
+          contents = [
+            {
+              source = bootScript;
+              target = "cygwin.ps1";
+            }
+          ];
+
+          storeContents = [
+            {
+              object = system;
+              symlink = "none";
+            }
+          ];
+
+          extraCommands = buildPackages.writeShellScript "extra-commands.sh" ''
+            chmod -R +w nix
+            mkdir -p tmp nix/var/nix/profiles dev
+            mkdir -m 01777 dev/{shm,mqueue}
+            ln -s "$(realpath -s --relative-to=/nix/var/nix/profiles "${system}")" nix/var/nix/profiles/system
+            find . -type l -print0 | while read -r -d "" f; do
+                symlinkTarget=$(readlink "$f")
+                if [[ "$symlinkTarget"/ != /nix/store* ]]; then
+                    # skip this symlink as it doesn't point to /nix/store
+                    continue
+                fi
+
+                relativeTarget=''${symlinkTarget#/}
+
+                if [ ! -e "$relativeTarget" ]; then
+                    echo "the symlink $f is broken, it points to $relativeTarget (which is missing)"
+                fi
+
+                relativeTarget=$(realpath -s --relative-to=$(dirname "$f") "$relativeTarget")
+
+                echo "changing symlink $f -> $symlinkTarget to $relativeTarget"
+                ln -snf "$relativeTarget" "$f"
+            done
+
+            mkdir -p "$out"/tarball
+            cp "${install}" "$out"/tarball/install.ps1
+            cp "${gnutar}/bin/tar.exe" "$out"/tarball/
+            for dll in "${gnutar}/bin"/*.dll; do
+              if [[ $dll != */cygwin1.dll ]]; then
+                cp "$dll" "$out"/tarball/
+              fi
+            done
+            cp "${cygwin1}" "$out"/tarball/
+          '';
+        });
+    };
+  };
+}
diff --git a/nixos/modules/config/nix.nix b/nixos/modules/config/nix.nix
index 9dfc4a1e664e7..bc30e9c5a2024 100644
--- a/nixos/modules/config/nix.nix
+++ b/nixos/modules/config/nix.nix
@@ -135,6 +135,24 @@ in
 
   options = {
     nix = {
+      enable = lib.mkOption {
+        type = lib.types.bool;
+        default = true;
+        description = ''
+          Whether to enable Nix.
+          Disabling Nix makes the system hard to modify and the Nix programs and configuration will not be made available by NixOS itself.
+        '';
+      };
+
+      package = lib.mkOption {
+        type = lib.types.package;
+        default = pkgs.nix;
+        defaultText = lib.literalExpression "pkgs.nix";
+        description = ''
+          This option specifies the Nix package instance to use throughout the system.
+        '';
+      };
+
       checkConfig = mkOption {
         type = types.bool;
         default = true;
diff --git a/nixos/modules/security/pam.nix b/nixos/modules/security/pam.nix
index 176a8e4c79eb8..243ee343db823 100644
--- a/nixos/modules/security/pam.nix
+++ b/nixos/modules/security/pam.nix
@@ -1656,6 +1656,10 @@ in
 
   options = {
 
+    security.pam.enable = lib.mkEnableOption "enable pam" // {
+      default = true;
+    };
+
     security.pam.package = lib.mkPackageOption pkgs "pam" { };
 
     security.pam.loginLimits = lib.mkOption {
@@ -2277,7 +2281,7 @@ in
 
   ###### implementation
 
-  config = {
+  config = lib.mkIf config.security.pam.enable {
     assertions = [
       {
         assertion = config.users.motd == "" || config.users.motdFile == null;
diff --git a/nixos/modules/services/system/nix-daemon.nix b/nixos/modules/services/system/nix-daemon.nix
index ef740b9ba8d94..ce09d339fb1f7 100644
--- a/nixos/modules/services/system/nix-daemon.nix
+++ b/nixos/modules/services/system/nix-daemon.nix
@@ -70,24 +70,6 @@ in
 
     nix = {
 
-      enable = lib.mkOption {
-        type = lib.types.bool;
-        default = true;
-        description = ''
-          Whether to enable Nix.
-          Disabling Nix makes the system hard to modify and the Nix programs and configuration will not be made available by NixOS itself.
-        '';
-      };
-
-      package = lib.mkOption {
-        type = lib.types.package;
-        default = pkgs.nix;
-        defaultText = lib.literalExpression "pkgs.nix";
-        description = ''
-          This option specifies the Nix package instance to use throughout the system.
-        '';
-      };
-
       daemonCPUSchedPolicy = lib.mkOption {
         type = lib.types.enum [
           "other"
diff --git a/nixos/modules/system/boot/systemd.nix b/nixos/modules/system/boot/systemd.nix
index 7a606afcdd9db..f76c6860f697a 100644
--- a/nixos/modules/system/boot/systemd.nix
+++ b/nixos/modules/system/boot/systemd.nix
@@ -240,6 +240,10 @@ in
 
   options.systemd = {
 
+    enable = mkEnableOption "enable systemd" // {
+      default = true;
+    };
+
     package = mkPackageOption pkgs "systemd" { };
 
     enableStrictShellChecks = mkEnableOption "" // {
@@ -484,7 +488,7 @@ in
 
   ###### implementation
 
-  config = {
+  config = mkIf cfg.enable {
 
     warnings =
       let
diff --git a/nixos/modules/system/boot/systemd/tmpfiles.nix b/nixos/modules/system/boot/systemd/tmpfiles.nix
index 12eca48f945d4..8b34ba7cf28d2 100644
--- a/nixos/modules/system/boot/systemd/tmpfiles.nix
+++ b/nixos/modules/system/boot/systemd/tmpfiles.nix
@@ -192,7 +192,7 @@ in
     };
   };
 
-  config = {
+  config = lib.mkIf config.systemd.enable {
     warnings =
       let
         paths = lib.filter (path: path != null && lib.hasPrefix "/etc/tmpfiles.d/" path) (
diff --git a/nixos/modules/system/boot/systemd/user.nix b/nixos/modules/system/boot/systemd/user.nix
index d9a9631fba92f..f9f52cc640363 100644
--- a/nixos/modules/system/boot/systemd/user.nix
+++ b/nixos/modules/system/boot/systemd/user.nix
@@ -191,7 +191,7 @@ in
     };
   };
 
-  config = {
+  config = lib.mkIf config.systemd.enable {
     systemd.additionalUpstreamSystemUnits = [
       "user.slice"
     ];
diff --git a/nixos/release.nix b/nixos/release.nix
index 0fcc22981be53..da1d79ffba2d9 100644
--- a/nixos/release.nix
+++ b/nixos/release.nix
@@ -456,6 +456,32 @@ rec {
         )
       );
 
+  cygwinTarball =
+    forMatchingSystems
+      [
+        "x86_64-linux"
+        "aarch64-linux"
+      ]
+      (
+        system:
+
+        hydraJob (
+          (import lib/eval-config.nix {
+            system = null;
+            modules = [
+              configuration
+              versionModule
+              ./maintainers/scripts/cygwin/system.nix
+              ./maintainers/scripts/cygwin/tarball.nix
+              {
+                nixpkgs.buildPlatform = lib.mkDefault system;
+                nixpkgs.hostPlatform = lib.mkDefault "x86_64-cygwin";
+              }
+            ];
+          }).config.system.cygwin.tarball
+        )
+      );
+
   # Ensure that all packages used by the minimal NixOS config end up in the channel.
   dummy = forAllSystems (
     system:
diff --git a/pkgs/applications/editors/vim/default.nix b/pkgs/applications/editors/vim/default.nix
index 809e9808b1bee..d10513080d252 100644
--- a/pkgs/applications/editors/vim/default.nix
+++ b/pkgs/applications/editors/vim/default.nix
@@ -78,20 +78,26 @@ stdenv.mkDerivation {
     substituteInPlace src/which.sh --replace '$PATH' '$HOST_PATH'
   '';
 
-  postInstall = ''
-    ln -s $out/bin/vim $out/bin/vi
-    mkdir -p $out/share/vim
-    cp "${vimrc}" $out/share/vim/vimrc
+  postInstall =
+    let
+      exeSuffix = stdenv.hostPlatform.extensions.executable;
+    in
+    ''
+      ln -s $out/bin/vim${exeSuffix} $out/bin/vi
+      mkdir -p $out/share/vim
+      cp "${vimrc}" $out/share/vim/vimrc
 
-    # Prevent bugs in the upstream makefile from silently failing and missing outputs.
-    # Some of those are build-time requirements for other packages.
-    for tool in ex xxd vi view vimdiff; do
-      if [ ! -e "$out/bin/$tool" ]; then
-        echo "ERROR: install phase did not install '$tool'."
-        exit 1
-      fi
-    done
-  '';
+      # Prevent bugs in the upstream makefile from silently failing and missing outputs.
+      # Some of those are build-time requirements for other packages.
+      for tool in ex xxd${exeSuffix} vi view vimdiff; do
+        if [ ! -e "$out/bin/$tool" ]; then
+          echo "ERROR: install phase did not install '$tool'."
+          exit 1
+        fi
+      done
+    '';
+
+  allowedImpureDLLs = [ "USER32.dll" ];
 
   __impureHostDeps = [ "/dev/ptmx" ];
 }
diff --git a/pkgs/applications/networking/sync/rsync/default.nix b/pkgs/applications/networking/sync/rsync/default.nix
index b98c39cc1baa3..30fdff8b49b64 100644
--- a/pkgs/applications/networking/sync/rsync/default.nix
+++ b/pkgs/applications/networking/sync/rsync/default.nix
@@ -10,7 +10,7 @@
   popt,
   enableACLs ? lib.meta.availableOn stdenv.hostPlatform acl,
   acl,
-  enableLZ4 ? true,
+  enableLZ4 ? !stdenv.hostPlatform.isCygwin,
   lz4,
   enableOpenSSL ? true,
   openssl,
@@ -80,7 +80,8 @@ stdenv.mkDerivation rec {
 
   passthru.tests = { inherit (nixosTests) rsyncd; };
 
-  doCheck = true;
+  # daemon and dir-sgid tests currently fail on cygwin
+  doCheck = !stdenv.buildPlatform.isCygwin;
 
   __darwinAllowLocalNetworking = true;
 
diff --git a/pkgs/build-support/bintools-wrapper/cygwin-ld-wrapper-hook.sh b/pkgs/build-support/bintools-wrapper/cygwin-ld-wrapper-hook.sh
new file mode 100644
index 0000000000000..8587b93cdd726
--- /dev/null
+++ b/pkgs/build-support/bintools-wrapper/cygwin-ld-wrapper-hook.sh
@@ -0,0 +1,8 @@
+for x in ${extraBefore+"${extraBefore[@]}"} \
+           ${params+"${params[@]}"} \
+           ${extraAfter+"${extraAfter[@]}"}; do
+  if [[ $x == --high-entropy-va ]]; then
+    echo "ld-wrapper: --high-entropy-va will cause instability on cygwin" >&2
+    exit 1
+  fi
+done
diff --git a/pkgs/build-support/bintools-wrapper/default.nix b/pkgs/build-support/bintools-wrapper/default.nix
index 8f5613e9e7bb5..3f87960fce50f 100644
--- a/pkgs/build-support/bintools-wrapper/default.nix
+++ b/pkgs/build-support/bintools-wrapper/default.nix
@@ -92,6 +92,7 @@ let
   # TODO(@Ericson2314) Make unconditional, or optional but always true by
   # default.
   targetPrefix = optionalString (targetPlatform != hostPlatform) (targetPlatform.config + "-");
+  exeSuffix = stdenvNoCC.hostPlatform.extensions.executable;
 
   bintoolsVersion = getVersion bintools;
   bintoolsName = removePrefix targetPrefix (getName bintools);
@@ -257,17 +258,17 @@ stdenvNoCC.mkDerivation {
   + ''
     for binary in objdump objcopy size strings as ar nm gprof dwp c++filt addr2line \
         ranlib readelf elfedit dlltool dllwrap windmc windres; do
-      if [ -e $ldPath/${targetPrefix}''${binary} ]; then
-        ln -s $ldPath/${targetPrefix}''${binary} $out/bin/${targetPrefix}''${binary}
+      if [ -e $ldPath/${targetPrefix}''${binary}${exeSuffix} ]; then
+        ln -s $ldPath/${targetPrefix}''${binary}${exeSuffix} $out/bin/${targetPrefix}''${binary}${exeSuffix}
       fi
     done
 
-    if [ -e ''${ld:-$ldPath/${targetPrefix}ld} ]; then
-      wrap ${targetPrefix}ld ${./ld-wrapper.sh} ''${ld:-$ldPath/${targetPrefix}ld}
+    if [ -e ''${ld:-$ldPath/${targetPrefix}ld}${exeSuffix} ]; then
+      wrap ${targetPrefix}ld ${./ld-wrapper.sh} ''${ld:-$ldPath/${targetPrefix}ld}${exeSuffix}
     fi
 
-    for variant in $ldPath/${targetPrefix}ld.*; do
-      basename=$(basename "$variant")
+    for variant in $ldPath/${targetPrefix}ld.*${exeSuffix}; do
+      basename=$(basename "${if exeSuffix != "" then "\${variant%${exeSuffix}}" else "$variant"}")
       wrap $basename ${./ld-wrapper.sh} $variant
     done
   '';
@@ -376,12 +377,12 @@ stdenvNoCC.mkDerivation {
       fi
     ''
 
-    + optionalString hostPlatform.isCygwin ''
-      hardening_unsupported_flags+=" pic"
+    + optionalString (targetPlatform.isAvr || targetPlatform.isWindows || targetPlatform.isCygwin) ''
+      hardening_unsupported_flags+=" relro bindnow"
     ''
 
-    + optionalString (targetPlatform.isAvr || targetPlatform.isWindows) ''
-      hardening_unsupported_flags+=" relro bindnow"
+    + optionalString targetPlatform.isCygwin ''
+      cp ${./cygwin-ld-wrapper-hook.sh} $out/nix-support/ld-wrapper-hook
     ''
 
     + optionalString (libc != null && targetPlatform.isAvr) ''
diff --git a/pkgs/build-support/cc-wrapper/default.nix b/pkgs/build-support/cc-wrapper/default.nix
index 07efab5e75c1e..fee4f8aea190b 100644
--- a/pkgs/build-support/cc-wrapper/default.nix
+++ b/pkgs/build-support/cc-wrapper/default.nix
@@ -118,6 +118,7 @@ let
   #
   # TODO(@Ericson2314) Make unconditional, or optional but always true by default.
   targetPrefix = optionalString (targetPlatform != hostPlatform) (targetPlatform.config + "-");
+  exeSuffix = stdenvNoCC.hostPlatform.extensions.executable;
 
   ccVersion = getVersion cc;
   ccName = removePrefix targetPrefix (getName cc);
@@ -524,34 +525,34 @@ stdenvNoCC.mkDerivation {
     export named_cc=${targetPrefix}cc
     export named_cxx=${targetPrefix}c++
 
-    if [ -e $ccPath/${targetPrefix}gcc ]; then
-      wrap ${targetPrefix}gcc $wrapper $ccPath/${targetPrefix}gcc
+    if [ -e $ccPath/${targetPrefix}gcc${exeSuffix} ]; then
+      wrap ${targetPrefix}gcc $wrapper $ccPath/${targetPrefix}gcc${exeSuffix}
       ln -s ${targetPrefix}gcc $out/bin/${targetPrefix}cc
       export named_cc=${targetPrefix}gcc
       export named_cxx=${targetPrefix}g++
-    elif [ -e $ccPath/clang ]; then
-      wrap ${targetPrefix}clang $wrapper $ccPath/clang
+    elif [ -e $ccPath/clang${exeSuffix} ]; then
+      wrap ${targetPrefix}clang $wrapper $ccPath/clang${exeSuffix}
       ln -s ${targetPrefix}clang $out/bin/${targetPrefix}cc
       export named_cc=${targetPrefix}clang
       export named_cxx=${targetPrefix}clang++
-    elif [ -e $ccPath/arocc ]; then
-      wrap ${targetPrefix}arocc $wrapper $ccPath/arocc
+    elif [ -e $ccPath/arocc${exeSuffix} ]; then
+      wrap ${targetPrefix}arocc $wrapper $ccPath/arocc${exeSuffix}
       ln -s ${targetPrefix}arocc $out/bin/${targetPrefix}cc
       export named_cc=${targetPrefix}arocc
     fi
 
-    if [ -e $ccPath/${targetPrefix}g++ ]; then
-      wrap ${targetPrefix}g++ $wrapper $ccPath/${targetPrefix}g++
+    if [ -e $ccPath/${targetPrefix}g++${exeSuffix} ]; then
+      wrap ${targetPrefix}g++ $wrapper $ccPath/${targetPrefix}g++${exeSuffix}
       ln -s ${targetPrefix}g++ $out/bin/${targetPrefix}c++
-    elif [ -e $ccPath/clang++ ]; then
-      wrap ${targetPrefix}clang++ $wrapper $ccPath/clang++
+    elif [ -e $ccPath/clang++${exeSuffix} ]; then
+      wrap ${targetPrefix}clang++ $wrapper $ccPath/clang++${exeSuffix}
       ln -s ${targetPrefix}clang++ $out/bin/${targetPrefix}c++
     fi
 
-    if [ -e $ccPath/${targetPrefix}cpp ]; then
-      wrap ${targetPrefix}cpp $wrapper $ccPath/${targetPrefix}cpp
-    elif [ -e $ccPath/cpp ]; then
-      wrap ${targetPrefix}cpp $wrapper $ccPath/cpp
+    if [ -e $ccPath/${targetPrefix}cpp${exeSuffix} ]; then
+      wrap ${targetPrefix}cpp $wrapper $ccPath/${targetPrefix}cpp${exeSuffix}
+    elif [ -e $ccPath/cpp${exeSuffix} ]; then
+      wrap ${targetPrefix}cpp $wrapper $ccPath/cpp${exeSuffix}
     fi
   ''
 
@@ -601,13 +602,18 @@ stdenvNoCC.mkDerivation {
       dontUnpack = true;
       installPhase =
         if targetPlatform.isCygwin then
-          ''
-            echo addToSearchPath "LINK_DLL_FOLDERS" "${cc_bin}/lib" >> $out
-            # Work around build failure caused by the gnulib workaround for
-            # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114870. remove after
-            # gnulib is updated in core packages (e.g. iconv, gnupatch, gnugrep)
-            echo appendToVar configureFlags gl_cv_clean_version_stddef=yes >> $out
-          ''
+          (
+            ''
+              echo addToSearchPath "_linkDeps_inputPath" "${cc_solib}/bin" >> $out
+              # Work around build failure caused by the gnulib workaround for
+              # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114870. remove after
+              # gnulib is updated in core packages (e.g. iconv, gnupatch, gnugrep)
+              echo appendToVar configureFlags gl_cv_clean_version_stddef=yes >> $out
+            ''
+            + lib.optionalString (hostPlatform.canExecute targetPlatform) ''
+              echo addToSearchPath "_PATH" "${cc_solib}/bin" >> $out
+            ''
+          )
         else
           ''
             echo addToSearchPath "LINK_DLL_FOLDERS" "${cc_solib}/lib" > $out
diff --git a/pkgs/build-support/lib/meson.nix b/pkgs/build-support/lib/meson.nix
index e6ae12392eecb..535344d177cf8 100644
--- a/pkgs/build-support/lib/meson.nix
+++ b/pkgs/build-support/lib/meson.nix
@@ -24,7 +24,9 @@ let
     needs_exe_wrapper = ${boolToString (!stdenv.buildPlatform.canExecute stdenv.hostPlatform)}
 
     [host_machine]
-    system = '${stdenv.targetPlatform.parsed.kernel.name}'
+    system = '${
+      if stdenv.targetPlatform.isCygwin then "cygwin" else stdenv.targetPlatform.parsed.kernel.name
+    }'
     cpu_family = '${cpuFamily stdenv.targetPlatform}'
     cpu = '${stdenv.targetPlatform.parsed.cpu.name}'
     endian = ${if stdenv.targetPlatform.isLittleEndian then "'little'" else "'big'"}
diff --git a/pkgs/build-support/setup-hooks/cygwin-dll-link.sh b/pkgs/build-support/setup-hooks/cygwin-dll-link.sh
deleted file mode 100644
index d5724794921dc..0000000000000
--- a/pkgs/build-support/setup-hooks/cygwin-dll-link.sh
+++ /dev/null
@@ -1,73 +0,0 @@
-addLinkDLLPaths() {
-    addToSearchPath "LINK_DLL_FOLDERS" "$1/lib"
-    addToSearchPath "LINK_DLL_FOLDERS" "$1/bin"
-}
-
-addEnvHooks "$targetOffset" addLinkDLLPaths
-
-addOutputDLLPaths() {
-  for output in $(getAllOutputNames); do
-    addToSearchPath "LINK_DLL_FOLDERS" "${!output}/lib"
-    addToSearchPath "LINK_DLL_FOLDERS" "${!output}/bin"
-  done
-}
-
-postInstallHooks+=(addOutputDLLPaths)
-
-_dllDeps() {
-    "$OBJDUMP" -p "$1" \
-        | sed -n 's/.*DLL Name: \(.*\)/\1/p' \
-        | sort -u
-}
-
-_linkDeps() {
-    local target="$1" dir="$2" check="$3"
-    echo 'target:' "$target"
-    local dll
-    _dllDeps "$target" | while read dll; do
-        echo '  dll:' "$dll"
-        if [[ -e "$dir/$dll" ]]; then continue; fi
-        # Locate the DLL - it should be an *executable* file on $LINK_DLL_FOLDERS.
-        local dllPath="$(PATH="$(dirname "$target"):$LINK_DLL_FOLDERS" type -P "$dll")"
-        if [[ -z "$dllPath" ]]; then
-          if [[ -z "$check" || -n "${allowedImpureDLLsMap[$dll]}" ]]; then
-             continue
-          fi
-          echo unable to find $dll in $LINK_DLL_FOLDERS >&2
-          exit 1
-        fi
-        echo '    linking to:' "$dllPath"
-        CYGWIN+=\ winsymlinks:nativestrict ln -sr "$dllPath" "$dir"
-        # That DLL might have its own (transitive) dependencies,
-        # so add also all DLLs from its directory to be sure.
-        _linkDeps "$dllPath" "$dir" ""
-    done
-}
-
-linkDLLs() {
-  if [ ! -d "$prefix" ]; then return; fi
-  (
-    set -e
-    shopt -s globstar nullglob
-
-    local -a allowedImpureDLLsArray
-    concatTo allowedImpureDLLsArray allowedImpureDLLs
-
-    local -A allowedImpureDLLsMap;
-
-    for dll in "${allowedImpureDLLsArray[@]}"; do
-      allowedImpureDLLsMap[$dll]=1
-    done
-
-    cd "$prefix"
-
-    # Iterate over any DLL that we depend on.
-    local target
-    for target in {bin,libexec}/**/*.{exe,dll}; do
-      [[ ! -f "$target" || ! -x "$target" ]] ||
-        _linkDeps "$target" "$(dirname "$target")" "1"
-    done
-  )
-}
-
-fixupOutputHooks+=(linkDLLs)
diff --git a/pkgs/build-support/setup-hooks/cygwin-dll-path.sh b/pkgs/build-support/setup-hooks/cygwin-dll-path.sh
new file mode 100644
index 0000000000000..27994475aa913
--- /dev/null
+++ b/pkgs/build-support/setup-hooks/cygwin-dll-path.sh
@@ -0,0 +1,10 @@
+# shellcheck shell=bash
+
+_addDLLPaths() {
+  # this reverts part of what strictDeps does, but this is needed for DLLs to be
+  # found before cygwin-dll-link runs
+  addToSearchPath "_PATH" "$1/bin"
+}
+
+# shellcheck disable=SC2154
+addEnvHooks "$targetOffset" _addDLLPaths
diff --git a/pkgs/by-name/bi/bison/package.nix b/pkgs/by-name/bi/bison/package.nix
index e5c6eef040ae4..88f8e5a19e2dd 100644
--- a/pkgs/by-name/bi/bison/package.nix
+++ b/pkgs/by-name/bi/bison/package.nix
@@ -48,7 +48,7 @@ stdenv.mkDerivation rec {
   doCheck = false;
   # Tests were disabled on LLVM/Darwin due to https://github.com/NixOS/nixpkgs/issues/463659
   # TODO: enable doInstallCheck unconditionally when fixed upstream.
-  doInstallCheck = !stdenv.cc.isClang;
+  doInstallCheck = !stdenv.cc.isClang && !stdenv.buildPlatform.isCygwin;
 
   meta = {
     homepage = "https://www.gnu.org/software/bison/";
diff --git a/pkgs/by-name/bm/bmake/package.nix b/pkgs/by-name/bm/bmake/package.nix
index 8c7c6841cf3e4..5f89824f21561 100644
--- a/pkgs/by-name/bm/bmake/package.nix
+++ b/pkgs/by-name/bm/bmake/package.nix
@@ -73,12 +73,20 @@ stdenv.mkDerivation (finalAttrs: {
   # * Disable deptgt-delete_on_error test (alpine does this too)
   # * Disable shell-ksh test (ksh doesn't compile with musl)
   # * Fix test failing due to different strerror(3) output for musl and glibc
-  postPatch = lib.optionalString (stdenv.hostPlatform.libc == "musl") ''
-    sed -i unit-tests/Makefile \
-      -e '/deptgt-delete_on_error/d' \
-      -e '/shell-ksh/d'
-    substituteInPlace unit-tests/opt-chdir.exp --replace "File name" "Filename"
-  '';
+  postPatch =
+    lib.optionalString (stdenv.hostPlatform.libc == "musl") ''
+      sed -i unit-tests/Makefile \
+        -e '/deptgt-delete_on_error/d' \
+        -e '/shell-ksh/d'
+      substituteInPlace unit-tests/opt-chdir.exp --replace "File name" "Filename"
+    ''
+    +
+      # this test doesn't give a permissions warning on cygwin
+      # TODO: find out why
+      lib.optionalString stdenv.hostPlatform.isCygwin ''
+        sed -i unit-tests/Makefile \
+          -e '/objdir-writable/d'
+      '';
 
   buildPhase = ''
     runHook preBuild
diff --git a/pkgs/by-name/ca/cacert/package.nix b/pkgs/by-name/ca/cacert/package.nix
index ccfb2b777d96d..3f42bb0e78235 100644
--- a/pkgs/by-name/ca/cacert/package.nix
+++ b/pkgs/by-name/ca/cacert/package.nix
@@ -94,23 +94,29 @@ stdenv.mkDerivation {
       --p11kit_output ca-bundle.trust.p11-kit
   '';
 
-  installPhase = ''
-    install -D -t "$out/etc/ssl/certs" ca-bundle.crt
-
-    # install standard PEM compatible bundle
-    install -D -t "$out/etc/ssl/certs" ca-no-trust-rules-bundle.crt
-
-    # install p11-kit specific output to p11kit output
-    install -D -t "$p11kit/etc/ssl/trust-source" ca-bundle.trust.p11-kit
-
-    # install individual certs in unbundled output
-    install -D -t "$unbundled/etc/ssl/certs" unbundled/*.crt
-
-    # install hashed certs in hashed output
-    # use cp as install doesn't copy symlinks
-    mkdir -p $hashed/etc/ssl/certs/
-    cp -P hashed/* $hashed/etc/ssl/certs/
-  '';
+  installPhase =
+    # on cygwin, globbing returns an invalid path when LANG is unset
+    # > install: cannot stat 'unbundled/NetLock_Arany_=Class_Gold=_F'$'\030''őtan'$'\372''s'$'\355''tv'$'\341''ny:49412ce40010.crt': No such file or directory
+    lib.optionalString stdenv.buildPlatform.isCygwin ''
+      export LANG=C
+    ''
+    + ''
+      install -D -t "$out/etc/ssl/certs" ca-bundle.crt
+
+      # install standard PEM compatible bundle
+      install -D -t "$out/etc/ssl/certs" ca-no-trust-rules-bundle.crt
+
+      # install p11-kit specific output to p11kit output
+      install -D -t "$p11kit/etc/ssl/trust-source" ca-bundle.trust.p11-kit
+
+      # install individual certs in unbundled output
+      install -D -t "$unbundled/etc/ssl/certs" unbundled/*.crt
+
+      # install hashed certs in hashed output
+      # use cp as install doesn't copy symlinks
+      mkdir -p $hashed/etc/ssl/certs/
+      cp -P hashed/* $hashed/etc/ssl/certs/
+    '';
 
   setupHook = ./setup-hook.sh;
 
diff --git a/pkgs/by-name/cm/cmake/package.nix b/pkgs/by-name/cm/cmake/package.nix
index 3f099d56c7f9f..2663187c76db6 100644
--- a/pkgs/by-name/cm/cmake/package.nix
+++ b/pkgs/by-name/cm/cmake/package.nix
@@ -124,14 +124,17 @@ stdenv.mkDerivation (finalAttrs: {
     ++ lib.optional cursesUI ncurses
     ++ lib.optional qt5UI qtbase;
 
-  preConfigure = ''
-    substituteInPlace Modules/Platform/UnixPaths.cmake \
-      --subst-var-by libc_bin ${lib.getBin stdenv.cc.libc} \
-      --subst-var-by libc_dev ${lib.getDev stdenv.cc.libc} \
-      --subst-var-by libc_lib ${lib.getLib stdenv.cc.libc}
-    # CC_FOR_BUILD and CXX_FOR_BUILD are used to bootstrap cmake
-    configureFlags="--parallel=''${NIX_BUILD_CORES:-1} CC=$CC_FOR_BUILD CXX=$CXX_FOR_BUILD $configureFlags $cmakeFlags"
-  '';
+  preConfigure =
+    lib.optionalString (stdenv.cc.libc != null) ''
+      substituteInPlace Modules/Platform/UnixPaths.cmake \
+        --subst-var-by libc_bin ${lib.getBin stdenv.cc.libc} \
+        --subst-var-by libc_dev ${lib.getDev stdenv.cc.libc} \
+        --subst-var-by libc_lib ${lib.getLib stdenv.cc.libc}
+    ''
+    + ''
+      # CC_FOR_BUILD and CXX_FOR_BUILD are used to bootstrap cmake
+      configureFlags="--parallel=''${NIX_BUILD_CORES:-1} CC=$CC_FOR_BUILD CXX=$CXX_FOR_BUILD $configureFlags $cmakeFlags"
+    '';
 
   # The configuration script is not autoconf-based, although being similar;
   # triples and other interesting info are passed via CMAKE_* environment
@@ -159,23 +162,31 @@ stdenv.mkDerivation (finalAttrs: {
     "--sphinx-info"
     "--sphinx-man"
   ]
-  ++ [
-    "--"
-    # We should set the proper `CMAKE_SYSTEM_NAME`.
-    # http://www.cmake.org/Wiki/CMake_Cross_Compiling
-    #
-    # Unfortunately cmake seems to expect absolute paths for ar, ranlib, and
-    # strip. Otherwise they are taken to be relative to the source root of the
-    # package being built.
-    (lib.cmakeFeature "CMAKE_CXX_COMPILER" "${stdenv.cc.targetPrefix}c++")
-    (lib.cmakeFeature "CMAKE_C_COMPILER" "${stdenv.cc.targetPrefix}cc")
-    (lib.cmakeFeature "CMAKE_AR" "${lib.getBin stdenv.cc.bintools.bintools}/bin/${stdenv.cc.targetPrefix}ar")
-    (lib.cmakeFeature "CMAKE_RANLIB" "${lib.getBin stdenv.cc.bintools.bintools}/bin/${stdenv.cc.targetPrefix}ranlib")
-    (lib.cmakeFeature "CMAKE_STRIP" "${lib.getBin stdenv.cc.bintools.bintools}/bin/${stdenv.cc.targetPrefix}strip")
-
-    (lib.cmakeBool "CMAKE_USE_OPENSSL" useOpenSSL)
-    (lib.cmakeBool "BUILD_CursesDialog" cursesUI)
-  ];
+  ++ (
+    let
+      cc = stdenv.cc;
+      bintools = lib.getBin (if cc.bintools.bintools != null then cc.bintools.bintools else cc.bintools);
+      targetPrefix = cc.targetPrefix;
+    in
+    [
+      "--"
+      # We should set the proper `CMAKE_SYSTEM_NAME`.
+      # http://www.cmake.org/Wiki/CMake_Cross_Compiling
+      #
+      # Unfortunately cmake seems to expect absolute paths for ar, ranlib, and
+      # strip. Otherwise they are taken to be relative to the source root of the
+      # package being built.
+      (lib.cmakeFeature "CMAKE_CXX_COMPILER" "${targetPrefix}c++")
+      (lib.cmakeFeature "CMAKE_C_COMPILER" "${targetPrefix}cc")
+      (lib.cmakeFeature "CMAKE_AR" "${bintools}/bin/${targetPrefix}ar")
+      (lib.cmakeFeature "CMAKE_RANLIB" "${bintools}/bin/${targetPrefix}ranlib")
+      (lib.cmakeFeature "CMAKE_STRIP" "${bintools}/bin/${targetPrefix}strip")
+
+      (lib.cmakeBool "CMAKE_USE_OPENSSL" useOpenSSL)
+      (lib.cmakeBool "BUILD_CursesDialog" cursesUI)
+    ]
+    ++ lib.optional stdenv.hostPlatform.isCygwin (lib.cmakeFeature "CMAKE_C_FLAGS" "-D_GNU_SOURCE")
+  );
 
   # make install attempts to use the just-built cmake
   preInstall = lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) ''
diff --git a/pkgs/by-name/cm/cmocka/fix-cygwin-build.patch b/pkgs/by-name/cm/cmocka/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..5e88d13b9c8d2
--- /dev/null
+++ b/pkgs/by-name/cm/cmocka/fix-cygwin-build.patch
@@ -0,0 +1,59 @@
+diff --git a/cmake/Modules/AddCMockaTest.cmake b/cmake/Modules/AddCMockaTest.cmake
+index 12fbd79..c619639 100644
+--- a/cmake/Modules/AddCMockaTest.cmake
++++ b/cmake/Modules/AddCMockaTest.cmake
+@@ -123,17 +123,21 @@ function(ADD_CMOCKA_TEST_ENVIRONMENT _TARGET_NAME)
+     if (WIN32 OR CYGWIN OR MINGW OR MSVC)
+         file(TO_NATIVE_PATH "${cmocka-library_BINARY_DIR}" CMOCKA_DLL_PATH)
+ 
+-        if (TARGET_SYSTEM_EMULATOR)
+-            set(DLL_PATH_ENV "WINEPATH=${CMOCKA_DLL_PATH};$ENV{WINEPATH}")
++        if (CYGWIN)
++            set(DLL_PATH_ENV "PATH=${CMOCKA_DLL_PATH}:$ENV{PATH}")
+         else()
+-            set(DLL_PATH_ENV "PATH=${CMOCKA_DLL_PATH}\\${CMAKE_BUILD_TYPE};$ENV{PATH}")
++            if (TARGET_SYSTEM_EMULATOR)
++                set(DLL_PATH_ENV "WINEPATH=${CMOCKA_DLL_PATH};$ENV{WINEPATH}")
++            else()
++                set(DLL_PATH_ENV "PATH=${CMOCKA_DLL_PATH}\\${CMAKE_BUILD_TYPE};$ENV{PATH}")
++            endif()
++            #
++            # IMPORTANT NOTE: The set_tests_properties(), below, internally
++            # stores its name/value pairs with a semicolon delimiter.
++            # because of this we must protect the semicolons in the path
++            #
++            string(REPLACE ";" "\\;" DLL_PATH_ENV "${DLL_PATH_ENV}")
+         endif()
+-        #
+-        # IMPORTANT NOTE: The set_tests_properties(), below, internally
+-        # stores its name/value pairs with a semicolon delimiter.
+-        # because of this we must protect the semicolons in the path
+-        #
+-        string(REPLACE ";" "\\;" DLL_PATH_ENV "${DLL_PATH_ENV}")
+ 
+         set_tests_properties(${_TARGET_NAME}
+                              PROPERTIES
+diff --git a/example/mock/chef_wrap/CMakeLists.txt b/example/mock/chef_wrap/CMakeLists.txt
+index 205ccd4..0b8b98d 100644
+--- a/example/mock/chef_wrap/CMakeLists.txt
++++ b/example/mock/chef_wrap/CMakeLists.txt
+@@ -15,6 +15,4 @@ set_target_properties(waiter_test_wrap
+         PROPERTIES
+         LINK_FLAGS  "-Wl,--wrap=chef_cook"
+ )
+-if (WIN32 OR MINGW OR CYGWIN)
+-    set_tests_properties(waiter_test_wrap PROPERTIES ENVIRONMENT "PATH=${DLL_PATH_ENV}")
+-endif (WIN32 OR MINGW OR CYGWIN)
++add_cmocka_test_environment(waiter_test_wrap)
+diff --git a/example/mock/uptime/CMakeLists.txt b/example/mock/uptime/CMakeLists.txt
+index 967185f..8e047e3 100644
+--- a/example/mock/uptime/CMakeLists.txt
++++ b/example/mock/uptime/CMakeLists.txt
+@@ -13,6 +13,7 @@ add_cmocka_test(test_uptime
+                 SOURCES test_uptime.c
+                 COMPILE_OPTIONS ${DEFAULT_C_COMPILE_FLAGS}
+                 LINK_LIBRARIES cmocka::cmocka)
++add_cmocka_test_environment(test_uptime)
+ set_property(TARGET
+                  test_uptime
+              PROPERTY
diff --git a/pkgs/by-name/cm/cmocka/package.nix b/pkgs/by-name/cm/cmocka/package.nix
index baeea60c9fcad..1b8772fb7fe8b 100644
--- a/pkgs/by-name/cm/cmocka/package.nix
+++ b/pkgs/by-name/cm/cmocka/package.nix
@@ -16,7 +16,8 @@ stdenv.mkDerivation rec {
 
   patches = [
     ./uintptr_t.patch
-  ];
+  ]
+  ++ lib.optional stdenv.hostPlatform.isCygwin ./fix-cygwin-build.patch;
 
   nativeBuildInputs = [ cmake ];
 
diff --git a/pkgs/by-name/co/cocom-tool-set/fix-cross-build.patch b/pkgs/by-name/co/cocom-tool-set/fix-cross-build.patch
new file mode 100644
index 0000000000000..252a50a06b2e4
--- /dev/null
+++ b/pkgs/by-name/co/cocom-tool-set/fix-cross-build.patch
@@ -0,0 +1,37 @@
+diff --git a/configure b/configure
+index bd6d039..64d1b17 100755
+--- a/configure
++++ b/configure
+@@ -5706,13 +5706,7 @@ if test $xnet = yes; then
+    SPECIAL_LINK_OPTION="$SPECIAL_LINK_OPTION -lxnet"
+ fi
+ 
+-if test "$cross_compiling" = yes; then
+-  { { echo "$as_me:$LINENO: error: cannot run test program while cross compiling
+-See \`config.log' for more details." >&5
+-echo "$as_me: error: cannot run test program while cross compiling
+-See \`config.log' for more details." >&2;}
+-   { (exit 1); exit 1; }; }
+-else
++if true; then
+   cat >conftest.$ac_ext <<_ACEOF
+ /* confdefs.h.  */
+ _ACEOF
+@@ -5775,7 +5775,7 @@ if test x$dino_shlib = x; then
+   echo +++We will not use DINO shared library
+   DINO_GCC_FPIC=-DNO_DINO_SHLIB
+   DINO_LIB_SUFFIX=a
+-  DINO_MAKELIB="ar rc \\\$\$0"
++  DINO_MAKELIB="$AR rc \\\$\$0"
+   DINO_AFTER_MAKELIB="$RANLIB \\\$\$0;echo \\\$\$0"
+   DINO_ADDITIONAL_LIBS="$DINO_LIB_NAME.$DINO_LIB_SUFFIX"
+   if test x$no_extern_shlib = x; then
+@@ -5790,7 +5790,7 @@ if test x$no_extern_shlib != x; then
+   EXTERN_GCC_FPIC=-DNO_EXTERN_SHLIB
+   DINO_GCC_FPIC="$DINO_GCC_FPIC -DNO_EXTERN_SHLIB"
+   EXTERN_LIB_SUFFIX=a
+-  EXTERN_MAKELIB="ar rc \\\$\$0"
++  EXTERN_MAKELIB="$AR rc \\\$\$0"
+   EXTERN_AFTER_MAKELIB="$RANLIB \\\$\$0;echo \\\$\$0"
+   DINO_ADDITIONAL_LIBS="$DINO_ADDITIONAL_LIBS mpi.$EXTERN_LIB_SUFFIX ieee.$EXTERN_LIB_SUFFIX ipcerr.$EXTERN_LIB_SUFFIX socket.$EXTERN_LIB_SUFFIX gmp.$EXTERN_LIB_SUFFIX"
+ else
diff --git a/pkgs/by-name/co/cocom-tool-set/package.nix b/pkgs/by-name/co/cocom-tool-set/package.nix
index 9ab545e01c4ff..750eafc072661 100644
--- a/pkgs/by-name/co/cocom-tool-set/package.nix
+++ b/pkgs/by-name/co/cocom-tool-set/package.nix
@@ -4,6 +4,7 @@
   fetchurl,
   autoreconfHook,
   bison,
+  buildPackages,
 }:
 stdenv.mkDerivation (finalAttrs: {
   pname = "cocom";
@@ -14,6 +15,17 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-4UOrVW15o17zHsHiQIl8m4qNC2aT5QorbkfX/UsgBRk=";
   };
 
+  patches = lib.optional (stdenv.buildPlatform != stdenv.hostPlatform) ./fix-cross-build.patch;
+
+  ${if (stdenv.buildPlatform != stdenv.hostPlatform) then "preConfigure" else null} =
+    lib.optionalString (stdenv.buildPlatform != stdenv.hostPlatform)
+      ''
+        substituteInPlace DINO/Makefile.in \
+          --replace-fail ../SPRUT/sprut "${buildPackages.cocom-tool-set}"/bin/sprut \
+          --replace-fail ../MSTA/msta "${buildPackages.cocom-tool-set}"/bin/msta \
+          --replace-fail ../SHILKA/shilka "${buildPackages.cocom-tool-set}"/bin/shilka
+      '';
+
   env = {
     RANLIB = "${stdenv.cc.targetPrefix}gcc-ranlib";
     NIX_CFLAGS_COMPILE = toString [
@@ -23,6 +35,11 @@ stdenv.mkDerivation (finalAttrs: {
     ];
   };
 
+  # cocom does $(DESTDIR)/$(libdir) which results in //nix/store/...
+  # on cygwin this is interpreted as a network path.
+  ${if stdenv.buildPlatform.isCygwin then "installFlags" else null} =
+    lib.optionalString stdenv.buildPlatform.isCygwin "DESTDIR=/.";
+
   autoreconfFlags = "REGEX";
 
   strictDeps = true;
diff --git a/pkgs/by-name/do/doctest/package.nix b/pkgs/by-name/do/doctest/package.nix
index 6eae43308fbfb..6aa3bdc8b3b4a 100644
--- a/pkgs/by-name/do/doctest/package.nix
+++ b/pkgs/by-name/do/doctest/package.nix
@@ -25,7 +25,12 @@ stdenv.mkDerivation rec {
       excludes = [ ".github/workflows/main.yml" ];
       hash = "sha256-kOBy0om6MPM2vLXZjNLXiezZqVgNr/viBI7mXrOZts8=";
     })
-  ];
+  ]
+  ++ lib.optional stdenv.hostPlatform.isCygwin (fetchpatch {
+    name = "doctest-fix-cygwin-tests.patch";
+    url = "https://github.com/doctest/doctest/commit/0e174a246558a8f5ef7299a3fd870c30281fd8d1.patch";
+    hash = "sha256-M7ByNFHCUb0ahsfNr4oUGTbR45qfdS9d5N8bGdQl/+Q=";
+  });
 
   nativeBuildInputs = [ cmake ];
 
diff --git a/pkgs/by-name/du/dumpnar/package.nix b/pkgs/by-name/du/dumpnar/package.nix
index a2206f68096f4..1dcefb39242e8 100644
--- a/pkgs/by-name/du/dumpnar/package.nix
+++ b/pkgs/by-name/du/dumpnar/package.nix
@@ -17,7 +17,7 @@ stdenv.mkDerivation {
 
   installPhase = ''
     mkdir -p $out/bin
-    cp dumpnar $out/bin/
+    cp dumpnar${stdenv.hostPlatform.extensions.executable} $out/bin/
   '';
 
   meta = {
diff --git a/pkgs/by-name/ed/ed/package.nix b/pkgs/by-name/ed/ed/package.nix
index 8e23c84e54fa0..b00ad47d7b114 100644
--- a/pkgs/by-name/ed/ed/package.nix
+++ b/pkgs/by-name/ed/ed/package.nix
@@ -31,7 +31,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   strictDeps = true;
 
-  doCheck = true;
+  doCheck = !stdenv.hostPlatform.isCygwin;
 
   passthru = {
     tests.version = testers.testVersion {
diff --git a/pkgs/by-name/gd/gdbm/package.nix b/pkgs/by-name/gd/gdbm/package.nix
index a31390c4ea3b9..90de4bd8b9b05 100644
--- a/pkgs/by-name/gd/gdbm/package.nix
+++ b/pkgs/by-name/gd/gdbm/package.nix
@@ -4,6 +4,7 @@
   stdenv,
   testers,
   updateAutotoolsGnuConfigScriptsHook,
+  autoconf,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -15,12 +16,18 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-aiRQShTeSnRBA9y5Nr6Xbfb76IzP8mBl5UwcR5RvSl4=";
   };
 
-  nativeBuildInputs = [ updateAutotoolsGnuConfigScriptsHook ];
+  nativeBuildInputs = [
+    updateAutotoolsGnuConfigScriptsHook
+  ]
+  # needed for testsuite.at patch below
+  ++ lib.optional stdenv.buildPlatform.isCygwin autoconf;
 
   hardeningDisable = [ "strictflexarrays3" ];
 
   configureFlags = [ (lib.enableFeature true "libgdbm-compat") ];
 
+  buildFlags = if stdenv.hostPlatform.isCygwin then "LDFLAGS=-no-undefined" else null;
+
   outputs = [
     "out"
     "dev"
@@ -42,7 +49,7 @@ stdenv.mkDerivation (finalAttrs: {
     substituteInPlace tests/Makefile.in \
       --replace-fail '_LDADD = ../src/libgdbm.la ../compat/libgdbm_compat.la' \
                      '_LDADD = ../compat/libgdbm_compat.la ../src/libgdbm.la'
-    substituteInPlace tests/testsuite.at
+    substituteInPlace tests/testsuite.at \
       --replace-fail 'm4_include([dbmfetch03.at])' ""
   '';
 
diff --git a/pkgs/by-name/gi/git/package.nix b/pkgs/by-name/gi/git/package.nix
index a1bc5aca526c3..7473ba7416e21 100644
--- a/pkgs/by-name/gi/git/package.nix
+++ b/pkgs/by-name/gi/git/package.nix
@@ -49,7 +49,7 @@
   withSsh ? false,
   sysctl,
   deterministic-host-uname, # trick Makefile into targeting the host platform when cross-compiling
-  doInstallCheck ? !stdenv.hostPlatform.isDarwin, # extremely slow on darwin
+  doInstallCheck ? !stdenv.hostPlatform.isDarwin && !stdenv.hostPlatform.isCygwin, # extremely slow on darwin and cygwin
   tests,
   rustSupport ? false,
   cargo,
@@ -559,6 +559,11 @@ stdenv.mkDerivation (finalAttrs: {
     # Fails largely due to assumptions about BOM
     # Tested to fail: 2.18.0
     disable_test t0028-working-tree-encoding
+  ''
+  + lib.optionalString stdenv.hostPlatform.isCygwin ''
+    disable_test t0006-date
+    disable_test t0610-reftable-basics
+    disable_test t6137-pathspec-wildcards-literal
   '';
 
   stripDebugList = [
diff --git a/pkgs/by-name/gr/groff/fix-cygwin-build.patch b/pkgs/by-name/gr/groff/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..ff63cd98e3c0d
--- /dev/null
+++ b/pkgs/by-name/gr/groff/fix-cygwin-build.patch
@@ -0,0 +1,159 @@
+diff --git a/Makefile.am b/Makefile.am
+index f7ab410..2b26b93 100644
+--- a/Makefile.am
++++ b/Makefile.am
+@@ -564,9 +564,9 @@ endif
+ 
+ # Path to binaries and flags used by contribs and doc to generated doc.
+ # These may be overridden if cross-compiling.
+-GROFFBIN = $(abs_top_builddir)/groff
++GROFFBIN = $(abs_top_builddir)/groff$(EXEEXT)
+ GROFF_BIN_PATH = $(abs_top_builddir)
+-PDFMOMBIN = $(abs_top_builddir)/pdfmom
++PDFMOMBIN = $(abs_top_builddir)/pdfmom$(EXEEXT)
+ # Search for macro files and device/font description directories in
+ # source _and_ build trees; some of each are generated.
+ FFLAG=-F$(abs_top_builddir)/font -F$(abs_top_srcdir)/font
+diff --git a/contrib/hdtbl/hdtbl.am b/contrib/hdtbl/hdtbl.am
+index 3dd60cf..e0dfa0c 100644
+--- a/contrib/hdtbl/hdtbl.am
++++ b/contrib/hdtbl/hdtbl.am
+@@ -119,8 +119,8 @@ SUFFIXES += .roff .in .ps
+ 	       -e "s|[@]EGREP[@]|$(EGREP)|" $< >$@
+ 
+ 
+-$(HDTBLPROCESSEDEXAMPLEFILES): $(DOC_GNU_EPS) groff troff eqn pic tbl \
+-  grops font/devps/stamp contrib/hdtbl/examples/common.roff
++$(HDTBLPROCESSEDEXAMPLEFILES): $(DOC_GNU_EPS) groff$(EXEEXT) troff$(EXEEXT) eqn$(EXEEXT) pic$(EXEEXT) tbl$(EXEEXT) \
++  grops$(EXEEXT) font/devps/stamp contrib/hdtbl/examples/common.roff
+ 
+ uninstall_groffdirs: uninstall-hdtbl-hook
+ uninstall-hdtbl-hook:
+diff --git a/contrib/mom/mom.am b/contrib/mom/mom.am
+index 3bbbc9a..7813699 100644
+--- a/contrib/mom/mom.am
++++ b/contrib/mom/mom.am
+@@ -145,7 +145,7 @@ SUFFIXES += .mom .pdf
+ 	&& LC_ALL=C $(MOMPDFMOM) $< >$@
+ 
+ $(MOMPROCESSEDEXAMPLEFILES): $(MOMNORMALFILES) \
+-  groff troff gropdf pdfmom penguin.ps penguin.pdf font/devpdf/stamp
++  groff$(EXEEXT) troff$(EXEEXT) gropdf$(EXEEXT) pdfmom$(EXEEXT) penguin.ps penguin.pdf font/devpdf/stamp
+ 
+ penguin.ps:
+ 	$(AM_V_at)cp $(mom_srcdir)/examples/penguin.ps $@
+diff --git a/contrib/pdfmark/pdfmark.am b/contrib/pdfmark/pdfmark.am
+index 15eec8c..2135450 100644
+--- a/contrib/pdfmark/pdfmark.am
++++ b/contrib/pdfmark/pdfmark.am
+@@ -68,7 +68,7 @@ contrib/pdfmark/pdfmark.pdf: contrib/pdfmark/pdfmark.ms
+ 	  $(top_srcdir)/contrib/pdfmark/pdfmark.ms >$@
+ 
+ # The pdf files use the local script to generate.
+-$(PDFDOCFILES): pdfroff groff troff gropdf
++$(PDFDOCFILES): pdfroff$(EXEEXT) groff$(EXEEXT) troff$(EXEEXT) gropdf$(EXEEXT)
+ $(PDFDOCFILES): $(dist_devpsfont_DATA) $(nodist_devpsfont_DATA) \
+   $(DOC_GNU_EPS)
+ 
+diff --git a/contrib/sboxes/sboxes.am b/contrib/sboxes/sboxes.am
+index 7786337..b2b93bb 100644
+--- a/contrib/sboxes/sboxes.am
++++ b/contrib/sboxes/sboxes.am
+@@ -54,7 +54,7 @@ $(sboxes_builddir)/msboxes.ms: $(SBOXES_EXAMPLEFILES) $(sboxesnotquine)
+ 	$(AM_V_GEN)mv $@.tmp $@
+ 
+ $(sboxes_builddir)/msboxes.pdf: $(sboxes_builddir)/msboxes.ms \
+-  $(dist_sboxestmac_DATA) groff troff gropdf font/devpdf/stamp
++  $(dist_sboxestmac_DATA) groff$(EXEEXT) troff$(EXEEXT) gropdf$(EXEEXT) font/devpdf/stamp
+ 	$(GROFF_V)$(DOC_GROFF) -M$(sboxes_srcdir) -ms -msboxes -Tpdf \
+ 	  $(sboxes_builddir)/msboxes.ms > $@
+ 
+diff --git a/doc/doc.am b/doc/doc.am
+index cddc519..a42622a 100644
+--- a/doc/doc.am
++++ b/doc/doc.am
+@@ -81,11 +81,11 @@ PROCESSEDDOCFILES = \
+   $(PROCESSEDDOCFILES_TXT)
+ 
+ # Declare minimal dependencies for documents by output driver.
+-PROCESSEDFILES_DEPS_HTML = pre-grohtml groff troff post-grohtml \
++PROCESSEDFILES_DEPS_HTML = pre-grohtml$(EXEEXT) groff$(EXEEXT) troff$(EXEEXT) post-grohtml$(EXEEXT) \
+   font/devhtml/stamp font/devps/stamp
+-PROCESSEDFILES_DEPS_PS = groff troff grops font/devps/stamp
+-PROCESSEDFILES_DEPS_PDF = groff troff gropdf font/devpdf/stamp
+-PROCESSEDFILES_DEPS_TXT = groff troff grotty font/devutf8/stamp
++PROCESSEDFILES_DEPS_PS = groff$(EXEEXT) troff$(EXEEXT) grops$(EXEEXT) font/devps/stamp
++PROCESSEDFILES_DEPS_PDF = groff$(EXEEXT) troff$(EXEEXT) gropdf$(EXEEXT) font/devpdf/stamp
++PROCESSEDFILES_DEPS_TXT = groff$(EXEEXT) troff$(EXEEXT) grotty$(EXEEXT) font/devutf8/stamp
+ 
+ if USE_GROHTML
+ $(PROCESSEDDOCFILES_HTML): $(PROCESSEDFILES_DEPS_HTML)
+@@ -254,7 +254,7 @@ man-clean:
+ # We embed the fonts (-P-e) to (1) honor the current PDF standard, (2)
+ # ensure consistent rendering of the document, and (3) exercise this
+ # feature of gropdf.
+-doc/groff-man-pages.pdf: $(GROFF_MAN_PAGES_ALL) eqn pic tbl \
++doc/groff-man-pages.pdf: $(GROFF_MAN_PAGES_ALL) eqn$(EXEEXT) pic$(EXEEXT) tbl$(EXEEXT) \
+   $(TMAC_PACKAGE_MAN) $(TMAC_PACKAGE_MDOC) font/devps/freeeuro.pfa
+ 	$(GROFF_V)$(DOC_GROFF) -pet -mandoc -dHF=HB -rC1 \
+ 	  -rCHECKSTYLE=3 -Tpdf -P-e \
+@@ -262,7 +262,7 @@ doc/groff-man-pages.pdf: $(GROFF_MAN_PAGES_ALL) eqn pic tbl \
+ 	  $(tmac_srcdir)/sv.tmac $(GROFF_MAN_PAGES2) \
+ 	  $(tmac_srcdir)/en.tmac $(GROFF_MAN_PAGES3) > $@
+ 
+-doc/groff-man-pages.utf8.txt: $(GROFF_MAN_PAGES_ALL) eqn pic tbl \
++doc/groff-man-pages.utf8.txt: $(GROFF_MAN_PAGES_ALL) eqn$(EXEEXT) pic$(EXEEXT) tbl$(EXEEXT) \
+   $(TMAC_PACKAGE_MAN) $(TMAC_PACKAGE_MDOC)
+ 	$(GROFF_V)$(DOC_GROFF) -pet -Tutf8 -mandoc \
+ 	  -rCHECKSTYLE=3 $(GROFF_MAN_PAGES1) \
+@@ -270,7 +270,7 @@ doc/groff-man-pages.utf8.txt: $(GROFF_MAN_PAGES_ALL) eqn pic tbl \
+ 	  $(tmac_srcdir)/en.tmac $(GROFF_MAN_PAGES3) > $@
+ 
+ doc/grnexmpl.ps: $(doc_srcdir)/grnexmpl.me $(doc_srcdir)/grnexmpl.g \
+-  grn eqn
++  grn$(EXEEXT) eqn$(EXEEXT)
+ 	$(GROFF_V)$(MKDIR_P) `dirname $@` \
+ 	&& $(DOC_GROFF) -Tps -ge -me $(doc_srcdir)/grnexmpl.me >$@
+ 
+@@ -334,19 +334,19 @@ SUFFIXES += .me.in .me
+ 
+ # Use '-K utf8', not '-k', in case 'configure' didn't find uchardet.
+ # The French translation uses tbl; its English counterpart does not.
+-doc/meintro_fr.ps: doc/meintro_fr.me preconv
++doc/meintro_fr.ps: doc/meintro_fr.me preconv$(EXEEXT)
+ 	$(GROFF_V)$(MKDIR_P) `dirname $@` \
+ 	&& $(DOC_GROFF) -K utf8 -t -Tps -me -mfr $< >$@
+ 
+-doc/ms.ps: $(doc_srcdir)/ms.ms eqn tbl
++doc/ms.ps: $(doc_srcdir)/ms.ms eqn$(EXEEXT) tbl$(EXEEXT)
+ 	$(GROFF_V)$(MKDIR_P) `dirname $@` \
+ 	&& $(DOC_GROFF) -et -Tps -ms $(doc_srcdir)/ms.ms >$@
+ 
+-doc/pic.ps: $(doc_srcdir)/pic.ms eqn pic tbl
++doc/pic.ps: $(doc_srcdir)/pic.ms eqn$(EXEEXT) pic$(EXEEXT) tbl$(EXEEXT)
+ 	$(GROFF_V)$(MKDIR_P) `dirname $@` \
+ 	&& $(DOC_GROFF) -pet -Tps -ms $(doc_srcdir)/pic.ms >$@
+ 
+-doc/webpage.ps: $(DOC_GNU_EPS) tmac/www.tmac tbl
++doc/webpage.ps: $(DOC_GNU_EPS) tmac/www.tmac tbl$(EXEEXT)
+ doc/webpage.ps: $(doc_srcdir)/webpage.ms
+ 	$(GROFF_V)$(MKDIR_P) `dirname $@` \
+ 	&& $(DOC_GROFF) -I $(doc_srcdir) -I $(doc_builddir) -t -Tps \
+@@ -357,7 +357,7 @@ doc/webpage.ps: $(doc_srcdir)/webpage.ms
+ #	$(GROFF_V)$(MKDIR_P) `dirname $@` \
+ #	&& $(DOC_GROFF) -Tps -ms $< >$@
+ 
+-doc/pic.html: eqn pic tbl
++doc/pic.html: eqn$(EXEEXT) pic$(EXEEXT) tbl$(EXEEXT)
+ doc/pic.html: tmac/www.tmac
+ doc/pic.html: $(doc_srcdir)/pic.ms
+ 	$(GROFF_V)$(MKDIR_P) $(doc_builddir) \
+@@ -365,7 +365,7 @@ doc/pic.html: $(doc_srcdir)/pic.ms
+ 	&& $(DOC_GROFF) -pet -P-Ipic -P-Dimg -P-jpic -Thtml -ms \
+ 	  $(doc_srcdir)/pic.ms > pic.html
+ 
+-doc/webpage.html: tbl
++doc/webpage.html: tbl$(EXEEXT)
+ doc/webpage.html: tmac/www.tmac
+ doc/webpage.html: $(DOC_GNU_EPS)
+ doc/webpage.html: $(doc_srcdir)/groff.css
diff --git a/pkgs/by-name/gr/groff/package.nix b/pkgs/by-name/gr/groff/package.nix
index ec203ed3902fd..784a4a3909265 100644
--- a/pkgs/by-name/gr/groff/package.nix
+++ b/pkgs/by-name/gr/groff/package.nix
@@ -38,7 +38,8 @@ stdenv.mkDerivation rec {
     # Backport e49b934 "Fix underspecified `getenv()` prototype." for non-glibc systems with C23
     # This can be dropped in the next release, when the local getopt implementation in libgroff is removed
     ./fix-underspecified-getenv-prototype.patch
-  ];
+  ]
+  ++ lib.optional stdenv.hostPlatform.isCygwin ./fix-cygwin-build.patch;
 
   outputs = [
     "out"
@@ -116,7 +117,9 @@ stdenv.mkDerivation rec {
     ]
     ++ lib.optionals (stdenv.buildPlatform != stdenv.hostPlatform) [
       "gl_cv_func_signbit=yes"
-    ];
+    ]
+    # src/libs/libgroff/getopt.c:125:14: error: conflicting types for 'getenv'; have 'char *(void)'
+    ++ lib.optional stdenv.hostPlatform.isCygwin "CFLAGS=-std=gnu17";
 
   makeFlags = lib.optionals (stdenv.buildPlatform != stdenv.hostPlatform) [
     # Trick to get the build system find the proper 'native' groff
diff --git a/pkgs/by-name/he/help2man/1.40.4-cygwin-nls.patch b/pkgs/by-name/he/help2man/1.40.4-cygwin-nls.patch
index 82f8cf1cb37bf..87591181983a7 100644
--- a/pkgs/by-name/he/help2man/1.40.4-cygwin-nls.patch
+++ b/pkgs/by-name/he/help2man/1.40.4-cygwin-nls.patch
@@ -11,16 +11,17 @@ that we're trying to help2man).
 
 --- help2man-1.46.5/Makefile.in	2014-10-09 13:03:01.000000000 +0200
 +++ help2man-1.46.5/Makefile.in	2015-05-12 14:46:52.995521900 +0200
-@@ -76,7 +76,8 @@
-        fi
+@@ -76,8 +76,9 @@
+ 	fi
 
- install_preload: install_dirs preload
+ install_preload: preload
+ 	$(MKINSTALLDIRS) $(DESTDIR)$(pkglibdir)
 -	$(INSTALL_PROGRAM) $(preload).so $(DESTDIR)$(pkglibdir)
 +	$(INSTALL_PROGRAM) lib/cygintl-9.dll $(DESTDIR)$(pkglibdir)
 +	ln -sf cygintl-9.dll $(DESTDIR)$(pkglibdir)/$(preload).so
 
- install_l10n: install_dirs msg_l10n man_l10n info_l10n
-        set -e; \
+ install_l10n: msg_l10n man_l10n info_l10n
+ 	set -e; \
 @@ -144,7 +146,9 @@
 
  preload: $(preload).so
diff --git a/pkgs/by-name/jq/jq/package.nix b/pkgs/by-name/jq/jq/package.nix
index b2a0941a79fe4..da568989ed917 100644
--- a/pkgs/by-name/jq/jq/package.nix
+++ b/pkgs/by-name/jq/jq/package.nix
@@ -79,7 +79,14 @@ stdenv.mkDerivation (finalAttrs: {
   ]
   ++ lib.optional (!onigurumaSupport) "--with-oniguruma=no"
   # jq is linked to libjq:
-  ++ lib.optional (!stdenv.hostPlatform.isDarwin) "LDFLAGS=-Wl,-rpath,\\\${libdir}";
+  ++ lib.optional (!stdenv.hostPlatform.isDarwin) "LDFLAGS=-Wl,-rpath,\\\${libdir}"
+  ++ lib.optionals stdenv.hostPlatform.isCygwin [
+    # these are both in -lm, but not in the headers, which confuses AC
+    "ac_cv_lib_m_scalb=no"
+    "ac_cv_lib_m_significand=no"
+  ];
+
+  makeFlags = if stdenv.hostPlatform.isCygwin then "libjq_la_LDFLAGS=-no-undefined" else null;
 
   # jq binary includes the whole `configureFlags` in:
   # https://github.com/jqlang/jq/commit/583e4a27188a2db097dd043dd203b9c106bba100
@@ -93,7 +100,9 @@ stdenv.mkDerivation (finalAttrs: {
       "$bin/bin/jq"
   '';
 
-  doInstallCheck = true;
+  doInstallCheck =
+    # shtest aborts: https://github.com/jqlang/jq/issues/3129
+    !stdenv.hostPlatform.isCygwin;
   installCheckTarget = "check";
 
   preInstallCheck = ''
diff --git a/pkgs/by-name/kr/krb5/package.nix b/pkgs/by-name/kr/krb5/package.nix
index 62b21154e65dc..ae158da4bbf7b 100644
--- a/pkgs/by-name/kr/krb5/package.nix
+++ b/pkgs/by-name/kr/krb5/package.nix
@@ -174,6 +174,9 @@ stdenv.mkDerivation rec {
     homepage = "http://web.mit.edu/kerberos/";
     license = lib.licenses.mit;
     platforms = lib.platforms.unix ++ lib.platforms.windows;
+    # configure: error: Shared libraries are not yet supported on this platform.
+    # cygwin has a large patchset for this package
+    broken = stdenv.hostPlatform.isCygwin;
   };
 
   passthru = {
diff --git a/pkgs/by-name/li/libarchive/fix-cygwin-build.patch b/pkgs/by-name/li/libarchive/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..d7947f62875b8
--- /dev/null
+++ b/pkgs/by-name/li/libarchive/fix-cygwin-build.patch
@@ -0,0 +1,64 @@
+--- origsrc/libarchive-3.8.1/libarchive/archive_platform.h	2025-03-20 10:48:34.000000000 +0100
++++ src/libarchive-3.8.1/libarchive/archive_platform.h	2025-03-29 08:56:00.759008500 +0100
+@@ -62,7 +62,7 @@
+ #endif
+ 
+ /* For cygwin, to avoid missing LONG, ULONG, PUCHAR, ... definitions */
+-#ifdef __CYGWIN__
++#ifdef __BOGUS_CYGWIN__
+ #include <windef.h>
+ #endif
+ 
+--- origsrc/libarchive-3.8.1/configure.ac
++++ src/libarchive-3.8.1/configure.ac
+@@ -93,13 +93,10 @@
+ 
+ dnl Compilation on mingw and Cygwin needs special Makefile rules
+ inc_windows_files=no
+-inc_cygwin_files=no
+ case "$host_os" in
+   *mingw* ) inc_windows_files=yes ;;
+-  *cygwin* | *msys*) inc_cygwin_files=yes ;;
+ esac
+ AM_CONDITIONAL([INC_WINDOWS_FILES], [test $inc_windows_files = yes])
+-AM_CONDITIONAL([INC_CYGWIN_FILES], [test $inc_cygwin_files = yes])
+ 
+ dnl Defines that are required for specific platforms (e.g. -D_POSIX_SOURCE, etc)
+ PLATFORMCPPFLAGS=
+@@ -256,7 +253,7 @@
+ 
+ # Set up defines needed before including any headers
+ case $host in
+-  *mingw* | *cygwin* | *msys*  )
++  *msys*  )
+   AC_PREPROC_IFELSE([AC_LANG_PROGRAM(
+     [[#include <windows.h>
+      #ifdef _WIN32_WINNT
+@@ -414,7 +411,7 @@
+ if test "x$with_bz2lib" != "xno"; then
+   AC_CHECK_HEADERS([bzlib.h])
+   case "$host_os" in
+-    *mingw* | *cygwin* | *msys*)
++    *mingw* | *msys*)
+       dnl AC_CHECK_LIB cannot be used on the Windows port of libbz2, therefore
+ 	  dnl use AC_LINK_IFELSE.
+ 	  AC_MSG_CHECKING([for BZ2_bzDecompressInit in -lbz2])
+@@ -1293,7 +1290,7 @@
+ ])
+ 
+ case "$host_os" in
+-  *mingw* | *cygwin* | *msys*)
++  *mingw* | *msys*)
+ 	;;
+   *)
+ 	CRYPTO_CHECK(MD5, LIBC, md5)
+@@ -1390,7 +1387,7 @@
+ fi
+ 
+ case "$host_os" in
+-  *mingw* | *cygwin* | *msys*)
++  *mingw* | *msys*)
+ 	CRYPTO_CHECK_WIN(MD5, CALG_MD5)
+ 	CRYPTO_CHECK_WIN(SHA1, CALG_SHA1)
+ 	CRYPTO_CHECK_WIN(SHA256, CALG_SHA_256)
+
diff --git a/pkgs/by-name/li/libarchive/package.nix b/pkgs/by-name/li/libarchive/package.nix
index b622460ec1b8c..3ea255beecdca 100644
--- a/pkgs/by-name/li/libarchive/package.nix
+++ b/pkgs/by-name/li/libarchive/package.nix
@@ -65,6 +65,12 @@ stdenv.mkDerivation (finalAttrs: {
         #   bsdcpio: linkfile: large inode number truncated: Numerical result out of range
         "cpio/test/test_basic.c"
         "cpio/test/test_format_newc.c"
+      ]
+      ++ lib.optionals stdenv.hostPlatform.isCygwin [
+        "libarchive/test/test_write_disk_lookup.c"
+        "cpio/test/test_owner_parse.c"
+        "cpio/test/test_option_c.c"
+        "cpio/test/test_option_L_upper.c"
       ];
       removeTest = testPath: ''
         substituteInPlace Makefile.am --replace-fail "${testPath}" ""
@@ -113,7 +119,10 @@ stdenv.mkDerivation (finalAttrs: {
   configureFlags = lib.optional (!xarSupport) "--without-xml2";
 
   # https://github.com/libarchive/libarchive/issues/1475
-  doCheck = !stdenv.hostPlatform.isMusl;
+  doCheck =
+    !stdenv.hostPlatform.isMusl
+    # TODO: investigate cygwin tests
+    && !stdenv.hostPlatform.isCygwin;
 
   preCheck = ''
     # Need an UTF-8 locale for test_I test.
diff --git a/pkgs/by-name/li/libcbor/package.nix b/pkgs/by-name/li/libcbor/package.nix
index c2445e7d8965e..bdfe9c20c3c8b 100644
--- a/pkgs/by-name/li/libcbor/package.nix
+++ b/pkgs/by-name/li/libcbor/package.nix
@@ -45,7 +45,11 @@ stdenv.mkDerivation (finalAttrs: {
 
   # Tests are restricted while pkgsStatic.cmocka is broken. Tracked at:
   # https://github.com/NixOS/nixpkgs/issues/213623
-  doCheck = !stdenv.hostPlatform.isStatic && stdenv.hostPlatform == stdenv.buildPlatform;
+  doCheck =
+    !stdenv.hostPlatform.isStatic
+    && stdenv.hostPlatform == stdenv.buildPlatform
+    # cygwin tests fail to link
+    && !stdenv.hostPlatform.isCygwin;
 
   nativeCheckInputs = [ cmocka ];
 
diff --git a/pkgs/by-name/li/libev/package.nix b/pkgs/by-name/li/libev/package.nix
index 86462cc5380f8..deeb6333ed6e1 100644
--- a/pkgs/by-name/li/libev/package.nix
+++ b/pkgs/by-name/li/libev/package.nix
@@ -5,7 +5,8 @@
   fetchpatch,
   updateAutotoolsGnuConfigScriptsHook,
   # Note: -static hasn’t work on darwin
-  static ? with stdenv.hostPlatform; isStatic && !isDarwin,
+  # cygwin requires libtool -no-undefined for shared
+  static ? with stdenv.hostPlatform; (isStatic && !isDarwin) || isCygwin,
 }:
 
 # Note: this package is used for bootstrapping fetchurl, and thus
diff --git a/pkgs/by-name/li/libfido2/package.nix b/pkgs/by-name/li/libfido2/package.nix
index 710960b91fb7a..7bc949e72f323 100644
--- a/pkgs/by-name/li/libfido2/package.nix
+++ b/pkgs/by-name/li/libfido2/package.nix
@@ -71,6 +71,12 @@ stdenv.mkDerivation rec {
   # causes possible redefinition of _FORTIFY_SOURCE?
   hardeningDisable = [ "fortify3" ];
 
+  allowedImpureDLLs = [
+    "HID.DLL"
+    "SETUPAPI.dll"
+    "USER32.dll"
+  ];
+
   meta = {
     description = ''
       Provides library functionality for FIDO 2.0, including communication with a device over USB.
diff --git a/pkgs/by-name/li/libgit2/package.nix b/pkgs/by-name/li/libgit2/package.nix
index 20655c7b77e1d..20b070359a7a3 100644
--- a/pkgs/by-name/li/libgit2/package.nix
+++ b/pkgs/by-name/li/libgit2/package.nix
@@ -82,6 +82,18 @@ stdenv.mkDerivation (finalAttrs: {
     # failed to set permissions on ...: Operation not permitted
     testArgs+=(-xrepo::init::extended_1)
     testArgs+=(-xrepo::template::extended_with_template_and_shared_mode)
+  ''
+  + lib.optionalString stdenv.buildPlatform.isCygwin ''
+    testArgs+=(
+      -xiterator::workdir::skips_unreadable_dirs
+      -xodb::loose::permissions_standard
+      -xodb::loose::permissions_readonly
+      -xodb::loose::permissions_readwrite
+      -xpack::packbuilder::permissions_readwrite
+      -xstatus::worktree::unreadable
+    )
+  ''
+  + ''
 
     (
       set -x
diff --git a/pkgs/by-name/lo/lowdown/package.nix b/pkgs/by-name/lo/lowdown/package.nix
index 684ca14b0cd9a..07842dd4fcae1 100644
--- a/pkgs/by-name/lo/lowdown/package.nix
+++ b/pkgs/by-name/lo/lowdown/package.nix
@@ -92,6 +92,16 @@ stdenv.mkDerivation rec {
     "install_static"
   ];
 
+  postInstall =
+    if stdenv.hostPlatform.isCygwin then
+      ''
+        mkdir -p "$lib"/bin
+        mv "$lib"/lib/*.dll "$lib"/bin/
+        chmod +x "$lib"/bin/*.dll
+      ''
+    else
+      null;
+
   doInstallCheck = !stdenv.hostPlatform.isDarwin || !enableDarwinSandbox;
   installCheckPhase = ''
     runHook preInstallCheck
diff --git a/pkgs/by-name/lz/lzip/package.nix b/pkgs/by-name/lz/lzip/package.nix
index 1d92e7e6439a6..0bfe47a8c0c44 100644
--- a/pkgs/by-name/lz/lzip/package.nix
+++ b/pkgs/by-name/lz/lzip/package.nix
@@ -23,7 +23,7 @@ stdenv.mkDerivation rec {
     hash = "sha256-CUGKbY+4P1ET9b2FbglwPfXTe64DCMZo0PNG49PwpW8=";
   };
 
-  patches = lib.optionals stdenv.hostPlatform.isMinGW [
+  patches = lib.optionals (stdenv.hostPlatform.isMinGW || stdenv.hostPlatform.isCygwin) [
     ./mingw-install-exe-file.patch
   ];
 
diff --git a/pkgs/by-name/ma/man-db/package.nix b/pkgs/by-name/ma/man-db/package.nix
index 0b173b013f7bf..48eea3fbfdefb 100644
--- a/pkgs/by-name/ma/man-db/package.nix
+++ b/pkgs/by-name/ma/man-db/package.nix
@@ -91,7 +91,12 @@ stdenv.mkDerivation rec {
     configureFlagsArray+=("--with-sections=1 n l 8 3 0 2 5 4 9 6 7")
   '';
 
-  postInstall = ''
+  ${if stdenv.hostPlatform.isCygwin then "postInstall" else null} = ''
+    mv "$out"/lib/bin/* "$out"/bin/
+    rmdir "$out"/lib/bin
+  '';
+
+  ${if stdenv.hostPlatform.isCygwin then "postFixup" else "postInstall"} = ''
     # apropos/whatis uses program name to decide whether to act like apropos or whatis
     # (multi-call binary). `apropos` is actually just a symlink to whatis. So we need to
     # make sure that we don't wrap symlinks (since that changes argv[0] to the -wrapped name)
diff --git a/pkgs/by-name/me/meson/package.nix b/pkgs/by-name/me/meson/package.nix
index 322bf863e0f90..20570bd0ea252 100644
--- a/pkgs/by-name/me/meson/package.nix
+++ b/pkgs/by-name/me/meson/package.nix
@@ -142,9 +142,15 @@ python3.pkgs.buildPythonApplication rec {
         # fails for unknown reason
         "test cases/python/4 custom target depends extmodule"
       ]
+      ++ lib.optionals stdenv.hostPlatform.isCygwin [
+        # fails for unknown reason
+        "test cases/common/122 no buildincdir"
+        "test cases/common/184 openmp"
+        "test cases/windows/8 find program"
+      ]
     ))
     ++ [
-      ''HOME="$TMPDIR" ${
+      ''HOME="$TMPDIR" ${if stdenv.hostPlatform.isCygwin then "CYGWIN=winsymlinks=native " else ""}${
         if python3.isPyPy then python3.interpreter else "python"
       } ./run_project_tests.py''
       "runHook postCheck"
diff --git a/pkgs/by-name/ni/ninja/fix-cygwin-build.patch b/pkgs/by-name/ni/ninja/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..04211bcf00949
--- /dev/null
+++ b/pkgs/by-name/ni/ninja/fix-cygwin-build.patch
@@ -0,0 +1,12 @@
+diff --git a/src/util.cc b/src/util.cc
+index aeb1ce4..876cc3d 100644
+--- a/src/util.cc
++++ b/src/util.cc
+@@ -17,6 +17,7 @@
+ #ifdef __CYGWIN__
+ #include <windows.h>
+ #include <io.h>
++#include <sched.h>
+ #elif defined( _WIN32)
+ #include <windows.h>
+ #include <io.h>
diff --git a/pkgs/by-name/ni/ninja/package.nix b/pkgs/by-name/ni/ninja/package.nix
index 6f15be615ace1..2625feb1f4334 100644
--- a/pkgs/by-name/ni/ninja/package.nix
+++ b/pkgs/by-name/ni/ninja/package.nix
@@ -40,6 +40,10 @@ stdenv.mkDerivation (finalAttrs: {
 
   depsBuildBuild = [ buildPackages.stdenv.cc ];
 
+  env = lib.optionalAttrs stdenv.hostPlatform.isCygwin {
+    NIX_CFLAGS_COMPILE = lib.optionalString stdenv.hostPlatform.isCygwin "-D_POSIX_C_SOURCE=200809L -D_GNU_SOURCE";
+  };
+
   nativeBuildInputs = [
     python3
     re2c
@@ -62,7 +66,8 @@ stdenv.mkDerivation (finalAttrs: {
       url = "https://github.com/ninja-build/ninja/commit/9cf13cd1ecb7ae649394f4133d121a01e191560b.patch";
       hash = "sha256-zlMs9LDJ2thtiSUjbsONyqoyYxrB/Ilt2Ljr0nCU6nQ=";
     })
-  ];
+  ]
+  ++ lib.optional stdenv.hostPlatform.isCygwin ./fix-cygwin-build.patch;
 
   postPatch = ''
     # write rebuild args to file after bootstrap
diff --git a/pkgs/by-name/op/opensp/package.nix b/pkgs/by-name/op/opensp/package.nix
index d376fbe329ddc..5280cdf0e2e6d 100644
--- a/pkgs/by-name/op/opensp/package.nix
+++ b/pkgs/by-name/op/opensp/package.nix
@@ -10,6 +10,7 @@
   automake,
   libtool,
   autoreconfHook,
+  updateAutotoolsGnuConfigScriptsHook,
 }:
 
 stdenv.mkDerivation rec {
@@ -48,9 +49,11 @@ stdenv.mkDerivation rec {
     sed -i -e 's/name="idm.*"//g' $out/share/doc/OpenSP/releasenotes.html
   '';
 
-  preConfigure = lib.optionalString stdenv.hostPlatform.isCygwin ''
-    autoreconf -fi
-  '';
+  preConfigure = "";
+
+  configureFlags =
+    # dcigettext.c:154:7: error: conflicting types for 'getcwd'; have 'char *(void)'
+    lib.optional stdenv.hostPlatform.isCygwin "CFLAGS=-std=gnu17";
 
   strictDeps = true;
 
@@ -61,12 +64,8 @@ stdenv.mkDerivation rec {
   ]
   # Clang 16 fails to build due to inappropriate definitions in the `config.h` generated by the
   # existing configure scripts. Regenerate them to make sure they detect its features correctly.
-  ++ lib.optional stdenv.cc.isClang autoreconfHook
-  ++ lib.optionals stdenv.hostPlatform.isCygwin [
-    autoconf
-    automake
-    libtool
-  ];
+  ++ lib.optional (stdenv.cc.isClang || stdenv.hostPlatform.isCygwin) autoreconfHook
+  ++ lib.optional stdenv.hostPlatform.isCygwin updateAutotoolsGnuConfigScriptsHook;
 
   env = lib.optionalAttrs stdenv.cc.isGNU {
     NIX_CFLAGS_COMPILE = "-fpermissive";
diff --git a/pkgs/by-name/pk/pkg-config-unwrapped/package.nix b/pkgs/by-name/pk/pkg-config-unwrapped/package.nix
index eace0aeab4447..7a5ad31463f9d 100644
--- a/pkgs/by-name/pk/pkg-config-unwrapped/package.nix
+++ b/pkgs/by-name/pk/pkg-config-unwrapped/package.nix
@@ -3,6 +3,7 @@
   stdenv,
   fetchurl,
   libiconv,
+  autoreconfHook,
   vanilla ? false,
 }:
 
@@ -29,6 +30,7 @@ stdenv.mkDerivation rec {
     ./gcc-15.patch
   ]
   ++ lib.optional (!vanilla) ./requires-private.patch
+  # this is done upstream in recent glib versions using meson
   ++ lib.optional stdenv.hostPlatform.isCygwin ./2.36.3-not-win32.patch;
 
   # These three tests fail due to a (desired) behavior change from our ./requires-private.patch
@@ -42,6 +44,12 @@ stdenv.mkDerivation rec {
       rm -f check/check-requires-private check/check-gtk check/missing
     '';
 
+  autoreconfFlags = if stdenv.hostPlatform.isCygwin then "glib" else null;
+
+  nativeBuildInputs =
+    # required for cygwin patch
+    lib.optional stdenv.hostPlatform.isCygwin autoreconfHook;
+
   buildInputs = [ libiconv ];
 
   configureFlags = [
diff --git a/pkgs/by-name/po/popt/1.16-cygwin.patch b/pkgs/by-name/po/popt/1.16-cygwin.patch
deleted file mode 100644
index 9c084f0b8eaac..0000000000000
--- a/pkgs/by-name/po/popt/1.16-cygwin.patch
+++ /dev/null
@@ -1,11 +0,0 @@
---- origsrc/poptconfig.c	2009-05-20 08:18:07.000000000 -0500
-+++ src/poptconfig.c	2012-03-29 18:13:46.869286100 -0500
-@@ -42,7 +42,7 @@ extern int glob_pattern_p (const char *_
- /*@=declundef =exportheader =incondefs =protoparammatch =redecl =type @*/
- #endif	/* __LCLINT__ */
- 
--#if !defined(__GLIBC__)
-+#if !defined(__GLIBC__) && !defined(__CYGWIN__)
- /* Return nonzero if PATTERN contains any metacharacters.
-    Metacharacters can be quoted with backslashes if QUOTE is nonzero.  */
- static int
diff --git a/pkgs/by-name/po/popt/1.16-vpath.patch b/pkgs/by-name/po/popt/1.16-vpath.patch
deleted file mode 100644
index 4cfa1c8fb4db3..0000000000000
--- a/pkgs/by-name/po/popt/1.16-vpath.patch
+++ /dev/null
@@ -1,34 +0,0 @@
---- origsrc/Doxyfile.in	2008-04-26 16:57:32.000000000 -0500
-+++ src/Doxyfile.in	2012-03-29 18:15:56.649709100 -0500
-@@ -460,14 +460,14 @@ WARN_LOGFILE           =
- # with spaces.
- 
- INPUT                  = \
--                        ./popt.c \
--                        ./popt.h \
--                        ./poptconfig.c \
--                        ./popthelp.c \
--                        ./poptint.c \
--                        ./poptint.h \
--                        ./poptparse.c \
--			./system.h
-+                        @srcdir@/popt.c \
-+                        @srcdir@/popt.h \
-+                        @srcdir@/poptconfig.c \
-+                        @srcdir@/popthelp.c \
-+                        @srcdir@/poptint.c \
-+                        @srcdir@/poptint.h \
-+                        @srcdir@/poptparse.c \
-+			@srcdir@/system.h
- 
- # If the value of the INPUT tag contains directories, you can use the 
- # FILE_PATTERNS tag to specify one or more wildcard pattern (like *.cpp 
-@@ -658,7 +658,7 @@ HTML_HEADER            =
- # each generated HTML page. If it is left blank doxygen will generate a 
- # standard footer.
- 
--HTML_FOOTER            = footer_no_timestamp.html
-+HTML_FOOTER            = @srcdir@/footer_no_timestamp.html
- 
- # The HTML_STYLESHEET tag can be used to specify a user-defined cascading 
- # style sheet that is used by each HTML page. It can be used to 
diff --git a/pkgs/by-name/po/popt/package.nix b/pkgs/by-name/po/popt/package.nix
index dffe05a33b420..fdb3d2fcc714e 100644
--- a/pkgs/by-name/po/popt/package.nix
+++ b/pkgs/by-name/po/popt/package.nix
@@ -17,29 +17,24 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ updateAutotoolsGnuConfigScriptsHook ];
 
-  patches =
-    lib.optionals stdenv.hostPlatform.isCygwin [
-      ./1.16-cygwin.patch
-      ./1.16-vpath.patch
-    ]
-    ++ lib.optionals stdenv.hostPlatform.isMinGW [
-      # Do not require <sys/ioctl.h>
-      (fetchpatch2 {
-        url = "https://aur.archlinux.org/cgit/aur.git/plain/get-w32-console-maxcols.mingw32.patch?h=mingw-w64-popt&id=63f2cdb0de116362c49681cef20f7a8b4355e85a";
-        sha256 = "zv43l1RBqNzT/JG+jQaMVFaFv+ZYPuIiAtKUDzJJBbc=";
-        stripLen = 1;
-        extraPrefix = "src/";
-      })
+  patches = lib.optionals stdenv.hostPlatform.isMinGW [
+    # Do not require <sys/ioctl.h>
+    (fetchpatch2 {
+      url = "https://aur.archlinux.org/cgit/aur.git/plain/get-w32-console-maxcols.mingw32.patch?h=mingw-w64-popt&id=63f2cdb0de116362c49681cef20f7a8b4355e85a";
+      sha256 = "zv43l1RBqNzT/JG+jQaMVFaFv+ZYPuIiAtKUDzJJBbc=";
+      stripLen = 1;
+      extraPrefix = "src/";
+    })
 
-      # Do not try to detect setuid, it is not a thing.
-      (fetchpatch2 {
-        url = "https://github.com/rpm-software-management/popt/commit/905544c5d9767894edaf71a1e3ce5126944c5695.patch";
-        sha256 = "3PmcxeiEZ/Hof0zoVFSytEXvQ8gE8Sp5UdagExPVICU=";
-        stripLen = 1;
-        extraPrefix = "src/";
-        revert = true;
-      })
-    ];
+    # Do not try to detect setuid, it is not a thing.
+    (fetchpatch2 {
+      url = "https://github.com/rpm-software-management/popt/commit/905544c5d9767894edaf71a1e3ce5126944c5695.patch";
+      sha256 = "3PmcxeiEZ/Hof0zoVFSytEXvQ8gE8Sp5UdagExPVICU=";
+      stripLen = 1;
+      extraPrefix = "src/";
+      revert = true;
+    })
+  ];
 
   doCheck = false; # fails
 
diff --git a/pkgs/by-name/to/toml11/package.nix b/pkgs/by-name/to/toml11/package.nix
index dd5924edd489b..5527949ee13ca 100644
--- a/pkgs/by-name/to/toml11/package.nix
+++ b/pkgs/by-name/to/toml11/package.nix
@@ -38,7 +38,11 @@ stdenv.mkDerivation (finalAttrs: {
   ];
   cmakeFlags = [
     (lib.cmakeBool "TOML11_BUILD_TOML_TESTS" finalAttrs.finalPackage.doCheck)
-  ];
+  ]
+  ++ lib.optional stdenv.hostPlatform.isCygwin (
+    lib.cmakeFeature "CMAKE_CXX_FLAGS" "-D_POSIX_C_SOURCE=200809L"
+  );
+
   checkInputs = [
     doctest
     nlohmann_json
diff --git a/pkgs/by-name/tz/tzdata/fix-cygwin-build.patch b/pkgs/by-name/tz/tzdata/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..022371afc5739
--- /dev/null
+++ b/pkgs/by-name/tz/tzdata/fix-cygwin-build.patch
@@ -0,0 +1,50 @@
+diff --git a/Makefile b/Makefile
+index 2130582..9a97470 100644
+--- a/Makefile
++++ b/Makefile
+@@ -642,7 +642,7 @@ VERSION_DEPS= \
+ 		ziguard.awk zishrink.awk \
+ 		zone.tab zone1970.tab zonenow.tab
+ 
+-all:		tzselect zic zdump libtz.a $(TABDATA) \
++all:		tzselect zic.exe zdump.exe libtz.a $(TABDATA) \
+ 		  vanguard.zi main.zi rearguard.zi
+ 
+ ALL:		all date $(ENCHILADA)
+@@ -658,8 +658,8 @@ install:	all $(DATA) $(REDO) $(MANS)
+ 			-t '$(DESTDIR)$(TZDEFAULT)'
+ 		cp -f $(TABDATA) '$(DESTDIR)$(TZDIR)/.'
+ 		cp tzselect '$(DESTDIR)$(BINDIR)/.'
+-		cp zdump '$(DESTDIR)$(ZDUMPDIR)/.'
+-		cp zic '$(DESTDIR)$(ZICDIR)/.'
++		cp zdump.exe '$(DESTDIR)$(ZDUMPDIR)/.'
++		cp zic.exe '$(DESTDIR)$(ZICDIR)/.'
+ 		cp libtz.a '$(DESTDIR)$(LIBDIR)/.'
+ 		$(RANLIB) '$(DESTDIR)$(LIBDIR)/libtz.a'
+ 		cp -f newctime.3 newtzset.3 '$(DESTDIR)$(MANDIR)/man3/.'
+@@ -727,10 +727,10 @@ version.h:	version
+ 		  >$@.out
+ 		mv $@.out $@
+ 
+-zdump:		$(TZDOBJS)
++zdump.exe:		$(TZDOBJS)
+ 		$(CC) -o $@ $(CFLAGS) $(LDFLAGS) $(TZDOBJS) $(LDLIBS)
+ 
+-zic:		$(TZCOBJS)
++zic.exe:		$(TZCOBJS)
+ 		$(CC) -o $@ $(CFLAGS) $(LDFLAGS) $(TZCOBJS) $(LDLIBS)
+ 
+ leapseconds:	$(LEAP_DEPS)
+diff --git a/private.h b/private.h
+index 074da28..6f8b50d 100644
+--- a/private.h
++++ b/private.h
+@@ -299,7 +299,7 @@ extern int optind;
+ #ifndef HAVE_ISSETUGID
+ # if (defined __FreeBSD__ || defined __NetBSD__ || defined __OpenBSD__ \
+       || (defined __linux__ && !defined __GLIBC__) /* Android, musl, etc. */ \
+-      || (defined __APPLE__ && defined __MACH__) || defined __sun)
++      || (defined __APPLE__ && defined __MACH__) || defined __sun || defined __CYGWIN__)
+ #  define HAVE_ISSETUGID 1
+ # else
+ #  define HAVE_ISSETUGID 0
diff --git a/pkgs/by-name/tz/tzdata/package.nix b/pkgs/by-name/tz/tzdata/package.nix
index 146b46dc230d2..5378cc27d32cb 100644
--- a/pkgs/by-name/tz/tzdata/package.nix
+++ b/pkgs/by-name/tz/tzdata/package.nix
@@ -23,9 +23,11 @@ stdenv.mkDerivation (finalAttrs: {
 
   sourceRoot = ".";
 
-  patches = lib.optionals stdenv.hostPlatform.isWindows [
-    ./0001-Add-exe-extension-for-MS-Windows-binaries.patch
-  ];
+  patches =
+    lib.optionals stdenv.hostPlatform.isWindows [
+      ./0001-Add-exe-extension-for-MS-Windows-binaries.patch
+    ]
+    ++ lib.optional stdenv.hostPlatform.isCygwin ./fix-cygwin-build.patch;
 
   outputs = [
     "out"
diff --git a/pkgs/by-name/un/unzip/fix-cygwin-build.patch b/pkgs/by-name/un/unzip/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..e53ba19428239
--- /dev/null
+++ b/pkgs/by-name/un/unzip/fix-cygwin-build.patch
@@ -0,0 +1,26 @@
+diff --git a/unix/unxcfg.h b/unix/unxcfg.h
+index bcdfe16..0e00744 100644
+--- a/unix/unxcfg.h
++++ b/unix/unxcfg.h
+@@ -107,6 +107,8 @@ typedef struct stat z_stat;
+ #  ifndef timezone
+ #    define timezone _timezone
+ #  endif
++#  include <utime.h>
++#  define GOT_UTIMBUF
+ #endif
+ 
+ #ifdef BSD
+diff --git a/unix/Makefile b/unix/Makefile
+index a0a6270..51f243d 100644
+--- a/unix/Makefile
++++ b/unix/Makefile
+@@ -125,7 +125,7 @@ prefix = /usr/local
+ BINDIR = $(prefix)/bin#			where to install executables
+ MANDIR = $(prefix)/man/man$(manext)#	where to install man pages
+ INSTALLEDBIN = $(BINDIR)/funzip$E $(BINDIR)/unzip$E $(BINDIR)/unzipsfx$E \
+-	$(BINDIR)/zipgrep$E $(BINDIR)/zipinfo$E
++	$(BINDIR)/zipgrep $(BINDIR)/zipinfo$E
+ INSTALLEDMAN = $(MANDIR)/funzip.$(manext) $(MANDIR)/unzip.$(manext) \
+ 	$(MANDIR)/unzipsfx.$(manext) $(MANDIR)/zipgrep.$(manext) \
+ 	$(MANDIR)/zipinfo.$(manext)
diff --git a/pkgs/by-name/un/unzip/package.nix b/pkgs/by-name/un/unzip/package.nix
index efe3226d6cdd0..c6fd0b33ee42e 100644
--- a/pkgs/by-name/un/unzip/package.nix
+++ b/pkgs/by-name/un/unzip/package.nix
@@ -67,7 +67,8 @@ stdenv.mkDerivation rec {
     url = "https://gitweb.gentoo.org/repo/gentoo.git/plain/app-arch/unzip/files/unzip-6.0-natspec.patch?id=56bd759df1d0c750a065b8c845e93d5dfa6b549d";
     name = "unzip-6.0-natspec.patch";
     sha256 = "67ab260ae6adf8e7c5eda2d1d7846929b43562943ec4aff629bd7018954058b1";
-  });
+  })
+  ++ lib.optional stdenv.hostPlatform.isCygwin ./fix-cygwin-build.patch;
 
   # gcc-15 uses c23 standard, which removed non-prototype function declarations.
   postPatch = ''
@@ -96,7 +97,8 @@ stdenv.mkDerivation rec {
 
   installFlags = [
     "prefix=${placeholder "out"}"
-  ];
+  ]
+  ++ lib.optional stdenv.hostPlatform.isCygwin "E=.exe";
 
   setupHook = ./setup-hook.sh;
 
diff --git a/pkgs/by-name/w3/w3m/fix-cygwin-build.patch b/pkgs/by-name/w3/w3m/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..39aa7d6d0fdd4
--- /dev/null
+++ b/pkgs/by-name/w3/w3m/fix-cygwin-build.patch
@@ -0,0 +1,34 @@
+diff --git a/config.h.in b/config.h.in
+index 623b5f9..26376fe 100644
+--- a/config.h.in
++++ b/config.h.in
+@@ -198,7 +198,6 @@
+ 
+ #if defined( __CYGWIN__ )
+ #define SUPPORT_NETBIOS_SHARE 1
+-#define SUPPORT_WIN9X_CONSOLE_MBCS 1
+ #endif
+ 
+ #if defined(__CYGWIN__) && defined(__x86_64__)
+diff --git a/terms.c b/terms.c
+index c77b87a..56b9306 100644
+--- a/terms.c
++++ b/terms.c
+@@ -2112,17 +2112,6 @@ term_title(const char *s)
+  * TERM=cygwin special handle announced deprecation and
+  * no one complains
+  */
+-#ifdef __CYGWIN__
+-	if (isLocalConsole && title_str == CYGWIN_TITLE) {
+-	    Str buff;
+-	    buff = Sprintf(title_str, s);
+-	    if (buff->length > 1024) {
+-		Strtruncate(buff, 1024);
+-	    }
+-	    SetConsoleTitle(buff->ptr);
+-	}
+-	else if (isLocalConsole || !isWinConsole)
+-#endif
+         fprintf(ttyf, title_str, s);
+     }
+ }
diff --git a/pkgs/by-name/w3/w3m/package.nix b/pkgs/by-name/w3/w3m/package.nix
index 73e82859bf633..fdc99ce10fc63 100644
--- a/pkgs/by-name/w3/w3m/package.nix
+++ b/pkgs/by-name/w3/w3m/package.nix
@@ -66,7 +66,8 @@ stdenv.mkDerivation (finalAttrs: {
   patches = [
     ./RAND_egd.libressl.patch
     ./https.patch
-  ];
+  ]
+  ++ lib.optional stdenv.hostPlatform.isCygwin ./fix-cygwin-build.patch;
 
   postPatch = lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) ''
     ln -s ${mktable}/bin/mktable mktable
@@ -117,6 +118,12 @@ stdenv.mkDerivation (finalAttrs: {
 
   enableParallelBuilding = false;
 
+  allowedImpureDLLs = [
+    "USER32.dll"
+    "GDI32.dll"
+    "gdiplus.dll"
+  ];
+
   passthru.tests.version = testers.testVersion {
     inherit (finalAttrs) version;
     package = w3m;
diff --git a/pkgs/development/compilers/gcc/common/builder.nix b/pkgs/development/compilers/gcc/common/builder.nix
index b1b5daeb00f1a..1e90828a6643d 100644
--- a/pkgs/development/compilers/gcc/common/builder.nix
+++ b/pkgs/development/compilers/gcc/common/builder.nix
@@ -363,6 +363,13 @@ originalAttrs:
           fi
       done
     ''
+    + lib.optionalString stdenv.targetPlatform.isCygwin ''
+      targetBinDir="''${targetConfig+$targetConfig/}bin"
+      for i in "''${!outputBin}/$targetLibDir"/cyg*.dll; do
+        mkdir -p "''${!outputLib}/$targetBinDir"
+        mv "$i" "''${!outputLib}/$targetBinDir"/
+      done
+    ''
     # if cross-compiling, link from $lib/lib to $lib/${targetConfig}.
     # since native-compiles have $lib/lib as a directory (not a
     # symlink), this ensures that in every case we can assume that
diff --git a/pkgs/development/compilers/gcc/common/configure-flags.nix b/pkgs/development/compilers/gcc/common/configure-flags.nix
index 98da0be6322e9..b112db0beea3c 100644
--- a/pkgs/development/compilers/gcc/common/configure-flags.nix
+++ b/pkgs/development/compilers/gcc/common/configure-flags.nix
@@ -176,7 +176,15 @@ let
       # We pick "/" path to effectively avoid sysroot offset and make it work
       # as a native case.
       # Darwin requires using the SDK as the sysroot for `SDKROOT` to work correctly.
-      "--with-build-sysroot=${if targetPlatform.isDarwin then apple-sdk.sdkroot else "/"}"
+      "--with-build-sysroot=${
+        if targetPlatform.isDarwin then
+          apple-sdk.sdkroot
+        else if buildPlatform.isCygwin then
+          # this avoids creating paths that start with //, which is a network path on cygwin
+          "/./"
+        else
+          "/"
+      }"
       # Same with the stdlibc++ headers embedded in the gcc output
       "--with-gxx-include-dir=${placeholder "out"}/include/c++/${version}/"
     ]
@@ -290,6 +298,9 @@ let
       # Workaround build failures like:
       #   cc1: error: fp software completion requires '-mtrap-precision=i' [-Werror]
       "--disable-werror"
+    ]
+    ++ lib.optionals targetPlatform.isCygwin [
+      "--enable-threads"
     ];
 
 in
diff --git a/pkgs/development/compilers/gcc/common/libgcc.nix b/pkgs/development/compilers/gcc/common/libgcc.nix
index c9f6a77933443..7f790d3d19607 100644
--- a/pkgs/development/compilers/gcc/common/libgcc.nix
+++ b/pkgs/development/compilers/gcc/common/libgcc.nix
@@ -58,6 +58,8 @@ lib.pipe drv
           && !stdenv.targetPlatform.isPE
           && !langJit
           && !stdenv.hostPlatform.isDarwin
+          # $libgcc logic is currently hardcoded for .so
+          && !stdenv.hostPlatform.isCygwin
           && enableShared
           && !useLibgccFromTargetLibc;
 
diff --git a/pkgs/development/compilers/gcc/default.nix b/pkgs/development/compilers/gcc/default.nix
index f7a19a73673b8..8f47dbca85dc7 100644
--- a/pkgs/development/compilers/gcc/default.nix
+++ b/pkgs/development/compilers/gcc/default.nix
@@ -36,7 +36,9 @@
   libucontext ? null,
   gnat-bootstrap ? null,
   enableMultilib ? false,
-  enablePlugin ? (lib.systems.equals stdenv.hostPlatform stdenv.buildPlatform), # Whether to support user-supplied plug-ins
+  enablePlugin ? (
+    lib.systems.equals stdenv.hostPlatform stdenv.buildPlatform && !stdenv.hostPlatform.isPE
+  ), # Whether to support user-supplied plug-ins
   name ? "gcc",
   libcCross ? null,
   threadsCross ? { }, # for MinGW
diff --git a/pkgs/development/compilers/gcc/patches/cygwin-allow-pic.patch b/pkgs/development/compilers/gcc/patches/cygwin-allow-pic.patch
new file mode 100644
index 0000000000000..fe5460285b44d
--- /dev/null
+++ b/pkgs/development/compilers/gcc/patches/cygwin-allow-pic.patch
@@ -0,0 +1,25 @@
+diff --git a/libgcc/config/i386/w32-unwind.h b/libgcc/config/i386/w32-unwind.h
+index c610c50cbd4..b9a6f336307 100644
+--- a/libgcc/config/i386/w32-unwind.h
++++ b/libgcc/config/i386/w32-unwind.h
+@@ -6,6 +6,7 @@ This file is part of GCC.
+ 
+ GCC is free software; you can redistribute it and/or modify it under
+ the terms of the GNU General Public License as published by the Free
++
+ Software Foundation; either version 3, or (at your option) any later
+ version.
+ 
+diff --git a/libiberty/configure b/libiberty/configure
+index 02fbaabe89e..7fe3ed3df1e 100755
+--- a/libiberty/configure
++++ b/libiberty/configure
+@@ -5336,8 +5336,6 @@ case "${host}" in
+     hppa*64*-*-hpux*)
+ 	# PIC is the default for 64-bit PA HP-UX.
+ 	;;
+-    i[34567]86-*-cygwin* | x86_64-*-cygwin*)
+-	;;
+     i[34567]86-*-mingw* | x86_64-*-mingw*)
+ 	;;
+     i[34567]86-*-interix[3-9]*)
diff --git a/pkgs/development/compilers/gcc/patches/cygwin-remove-relative-w32api-paths.patch b/pkgs/development/compilers/gcc/patches/cygwin-remove-relative-w32api-paths.patch
new file mode 100644
index 0000000000000..7f9fd7e606935
--- /dev/null
+++ b/pkgs/development/compilers/gcc/patches/cygwin-remove-relative-w32api-paths.patch
@@ -0,0 +1,12 @@
+diff --git a/gcc/config/i386/cygwin.h b/gcc/config/i386/cygwin.h
+index 93b279d0a92..a266eaabb9c 100644
+--- a/gcc/config/i386/cygwin.h
++++ b/gcc/config/i386/cygwin.h
+@@ -32,7 +32,6 @@ along with GCC; see the file COPYING3.  If not see
+ #define CPP_SPEC "%(cpp_cpu) %{posix:-D_POSIX_SOURCE} \
+   %{pthread:-D_REENTRANT} \
+   %{mwin32:-DWIN32 -D_WIN32 -D__WIN32 -D__WIN32__ %{!ansi:-DWINNT}} \
+-  %{!nostdinc:%{!mno-win32:-idirafter ../include/w32api%s -idirafter ../../include/w32api%s}}\
+ "
+ 
+ #undef STARTFILE_SPEC
diff --git a/pkgs/development/compilers/gcc/patches/default.nix b/pkgs/development/compilers/gcc/patches/default.nix
index 92369c5d0c609..b0da37f38d01b 100644
--- a/pkgs/development/compilers/gcc/patches/default.nix
+++ b/pkgs/development/compilers/gcc/patches/default.nix
@@ -248,4 +248,9 @@ optionals noSysDirs (
     url = "https://inbox.sourceware.org/gcc-patches/20250922182808.2599390-3-corngood@gmail.com/raw";
     hash = "sha256-8I2G4430gkYoWgUued4unqhk8ZCajHf1dcivAeuLZ0E=";
   })
+  ./cygwin-remove-relative-w32api-paths.patch
+]
+
+++ optionals hostPlatform.isCygwin [
+  ./cygwin-allow-pic.patch
 ]
diff --git a/pkgs/development/interpreters/perl/cygwin.c-fix-several-silly-terrible-C-errors.patch b/pkgs/development/interpreters/perl/cygwin.c-fix-several-silly-terrible-C-errors.patch
new file mode 100644
index 0000000000000..e31b4f6c58e6e
--- /dev/null
+++ b/pkgs/development/interpreters/perl/cygwin.c-fix-several-silly-terrible-C-errors.patch
@@ -0,0 +1,179 @@
+From b872e74120c4245132e2c906399bff9fc18e032d Mon Sep 17 00:00:00 2001
+From: Lukas Mai <lukasmai.403@gmail.com>
+Date: Wed, 6 Nov 2024 22:58:05 +0100
+Subject: [PATCH] cygwin.c: fix several silly/terrible C errors
+
+Errors fixed:
+
+Not detected by the compiler, but the preprocessor version checks only
+looked at `CYGWIN_VERSION_API_MINOR`, ignoring
+`CYGWIN_VERSION_API_MAJOR`.
+
+    cygwin.c: In function 'utf8_to_wide_extra_len':
+    cygwin.c:187:18: warning: initialization of 'size_t' {aka 'long unsigned int'} from 'size_t *' {aka 'long unsigned int *'} makes integer from pointer without a cast [-Wint-conversion]
+      187 |     Size_t len = strlen(buf) + extra_len + 1;
+          |                  ^~~~~~
+
+`extra_len` was declared as a pointer, but used as an integer. I don't
+see how this could have ever worked.
+
+    cygwin.c: In function 'S_convert_path_common':
+    cygwin.c:339:38: warning: 'realloc' called on unallocated object 'wconverted' [-Wfree-nonheap-object]
+      339 |             wconverted = (wchar_t *) realloc(&wconverted, newlen);
+          |                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    cygwin.c:357:39: warning: 'realloc' called on unallocated object 'converted_path' [-Wfree-nonheap-object]
+      357 |             converted_path = (char *) realloc(&converted_path, newlen);
+          |                                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Again, I don't see how this could have ever worked. We're passing the
+address of a local (stack) variable to `realloc` (instead of the value
+of the variable).
+
+    cygwin.c: In function 'wide_to_utf8':
+    cygwin.c:173:32: warning: pointer targets in passing argument 3 of 'Perl_utf16_to_utf8_base' differ in signedness [-Wpointer-sign]
+      173 |     utf16_to_utf8((U8 *) wsrc, buf, wlen, &blen);
+          |                                ^~~
+          |                                |
+          |                                char *
+
+The argument is declared as `U8 *`, so this is mostly harmless, but a
+cast silences the warning anyway.
+
+    cygwin.c: In function 'utf8_to_wide_extra_len':
+    cygwin.c:194:19: warning: passing argument 2 of 'Perl_utf8_to_utf16_base' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
+      194 |     utf8_to_utf16(buf, (U8 *) wsrc, len, &wlen);
+          |                   ^~~
+
+This is arguably a bug in `utf8_to_utf16`, which doesn't declare its
+input argument as pointer-to-const. But it's also a `char *` vs `U8 *`
+type mismatch, so a cast silences both issues.
+
+    cygwin.c: In function 'S_convert_path_common':
+    cygwin.c:292:22: warning: initialization discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
+      292 |         char *name = (direction == to_posix)
+          |                      ^
+
+This is a missing `const` in the declaration of a variable that points
+to string literals.
+---
+ cygwin/cygwin.c | 29 +++++++++++++++--------------
+ 1 file changed, 15 insertions(+), 14 deletions(-)
+
+diff --git a/cygwin/cygwin.c b/cygwin/cygwin.c
+index 7c3d5dc48c..625777366c 100644
+--- a/cygwin/cygwin.c
++++ b/cygwin/cygwin.c
+@@ -15,7 +15,10 @@
+ #include <mntent.h>
+ #include <alloca.h>
+ #include <dlfcn.h>
+-#if (CYGWIN_VERSION_API_MINOR >= 181)
++#define HAVE_CYGWIN_VERSION(MAJOR, MINOR) \
++    (CYGWIN_VERSION_API_MAJOR > (MAJOR) || \
++        (CYGWIN_VERSION_API_MAJOR == (MAJOR) && CYGWIN_VERSION_API_MINOR >= (MINOR)))
++#if HAVE_CYGWIN_VERSION(0, 181)
+ #include <wchar.h>
+ #endif
+ 
+@@ -158,7 +161,7 @@ leave:
+     return result;
+ }
+ 
+-#if (CYGWIN_VERSION_API_MINOR >= 181)
++#if HAVE_CYGWIN_VERSION(0, 181)
+ char*
+ wide_to_utf8(const wchar_t *wsrc)
+ {
+@@ -170,13 +173,13 @@ wide_to_utf8(const wchar_t *wsrc)
+ 
+     char *buf = (char *) safemalloc(blen);
+ 
+-    utf16_to_utf8((U8 *) wsrc, buf, wlen, &blen);
++    utf16_to_utf8((U8 *) wsrc, (U8 *) buf, wlen, &blen);
+ 
+     return buf;
+ }
+ 
+ wchar_t*
+-utf8_to_wide_extra_len(const char *buf, Size_t *extra_len)
++utf8_to_wide_extra_len(const char *buf, Size_t extra_len)
+ {
+     /* Return the conversion to UTF-16 of the UTF-8 string 'buf'
+      * (terminated by a NUL), making sure to have space for at least *extra_len
+@@ -191,7 +194,7 @@ utf8_to_wide_extra_len(const char *buf, Size_t *extra_len)
+ 
+     wchar_t* wsrc = (wchar_t *) safemalloc(wlen);
+ 
+-    utf8_to_utf16(buf, (U8 *) wsrc, len, &wlen);
++    utf8_to_utf16((U8 *) buf, (U8 *) wsrc, len, &wlen);
+ 
+     return wsrc;
+ }
+@@ -199,9 +202,7 @@ utf8_to_wide_extra_len(const char *buf, Size_t *extra_len)
+ wchar_t*
+ utf8_to_wide(const char *buf)
+ {
+-    Size_t extra_len = 0;
+-
+-    return utf8_to_wide_extra_len(buf, &extra_len);
++    return utf8_to_wide_extra_len(buf, 0);
+ }
+ 
+ #endif /* cygwin 1.7 */
+@@ -255,7 +256,7 @@ XS(XS_Cygwin_winpid_to_pid)
+ 
+     pid = (pid_t)SvIV(ST(0));
+ 
+-#if (CYGWIN_VERSION_API_MINOR >= 181)
++#if HAVE_CYGWIN_VERSION(0, 181)
+     RETVAL = cygwin_winpid_to_pid(pid);
+ #else
+     RETVAL = cygwin32_winpid_to_pid(pid);
+@@ -289,7 +290,7 @@ S_convert_path_common(pTHX_ const direction_t direction)
+     int isutf8 = 0;
+ 
+     if (items < 1 || items > 2) {
+-        char *name = (direction == to_posix)
++        const char *name = (direction == to_posix)
+                      ? "win::win_to_posix_path"
+                      : "posix_to_win_path";
+         Perl_croak(aTHX_ "Usage: Cygwin::%s(pathname, [absolute])", name);
+@@ -303,7 +304,7 @@ S_convert_path_common(pTHX_ const direction_t direction)
+         Perl_croak(aTHX_ "can't convert empty path");
+     isutf8 = SvUTF8(ST(0));
+ 
+-#if (CYGWIN_VERSION_API_MINOR >= 181)
++#if HAVE_CYGWIN_VERSION(0, 181)
+     /* Check utf8 flag and use wide api then.
+        Size calculation: On overflow let cygwin_conv_path calculate the final size.
+      */
+@@ -322,7 +323,7 @@ S_convert_path_common(pTHX_ const direction_t direction)
+ 
+         if (LIKELY(! IN_BYTES)) {    /* Normal case, convert UTF-8 to UTF-16 */
+             wlen = PATH_LEN_GUESS;
+-            wsrc = utf8_to_wide_extra_len(src_path, &wlen);
++            wsrc = utf8_to_wide_extra_len(src_path, wlen);
+             which_src = wsrc;
+         }
+         else { /* use bytes; assume already UTF-16 encoded bytestream */
+@@ -336,7 +337,7 @@ S_convert_path_common(pTHX_ const direction_t direction)
+ 
+         if (err == ENOSPC) { /* our space assumption was wrong, not enough space */
+             int newlen = cygwin_conv_path(what, which_src, wconverted, 0);
+-            wconverted = (wchar_t *) realloc(&wconverted, newlen);
++            wconverted = (wchar_t *) realloc(wconverted, newlen);
+             err = cygwin_conv_path(what, which_src, wconverted, newlen);
+         }
+ 
+@@ -354,7 +355,7 @@ S_convert_path_common(pTHX_ const direction_t direction)
+         err = cygwin_conv_path(what, src_path, converted_path, len + PATH_LEN_GUESS);
+         if (err == ENOSPC) { /* our space assumption was wrong, not enough space */
+             int newlen = cygwin_conv_path(what, src_path, converted_path, 0);
+-            converted_path = (char *) realloc(&converted_path, newlen);
++            converted_path = (char *) realloc(converted_path, newlen);
+             err = cygwin_conv_path(what, src_path, converted_path, newlen);
+         }
+     }
+-- 
+2.50.1
+
diff --git a/pkgs/development/interpreters/perl/fix-cygwin-cross.patch b/pkgs/development/interpreters/perl/fix-cygwin-cross.patch
new file mode 100644
index 0000000000000..fb8cb78b3b3cb
--- /dev/null
+++ b/pkgs/development/interpreters/perl/fix-cygwin-cross.patch
@@ -0,0 +1,27 @@
+diff --git a/cnf/configure_tool.sh b/cnf/configure_tool.sh
+index 2f5492e..85c9715 100644
+--- a/cnf/configure_tool.sh
++++ b/cnf/configure_tool.sh
+@@ -246,6 +246,10 @@ if not hinted 'osname'; then
+ 			define osname "MSWin32"
+ 			result "MSWin32"
+ 			;;
++		*-cygwin)
++			define osname "cygwin"
++			result "Cygwin"
++			;;
+ 		*-android|*-androideabi)
+ 			define osname "android"
+ 			result "Android"
+diff --git a/cnf/configure_func.sh b/cnf/configure_func.sh
+index b24fe03..00a217f 100644
+--- a/cnf/configure_func.sh
++++ b/cnf/configure_func.sh
+@@ -191,6 +191,7 @@ checkfunc d_msgrcv 'msgrcv' '0,NULL,0,0,0' 'sys/msg.h'
+ checkfunc d_msgsnd 'msgsnd' '0,NULL,0,0' 'sys/msg.h'
+ checkfunc d_msync 'msync' 'NULL,0,0' 'sys/mman.h'
+ checkfunc d_munmap 'munmap' 'NULL,0' 'sys/mman.h'
++checkfunc d_nanosleep 'nanosleep' 'NULL,NULL' 'time.h'
+ checkfunc d_newlocale 'newlocale' '0,NULL,0' 'locale.h'
+ checkfunc d_nice 'nice' '0' 'unistd.h'
+ checkfunc d_nl_langinfo 'nl_langinfo' '0' 'langinfo.h'
diff --git a/pkgs/development/interpreters/perl/interpreter.nix b/pkgs/development/interpreters/perl/interpreter.nix
index a501b99967253..3839acfd6bcbb 100644
--- a/pkgs/development/interpreters/perl/interpreter.nix
+++ b/pkgs/development/interpreters/perl/interpreter.nix
@@ -77,7 +77,8 @@ let
   # binary as early.
   #
   # Some more details: https://arsv.github.io/perl-cross/modules.html
-  ++ lib.optional crossCompiling ./cross.patch;
+  ++ lib.optional crossCompiling ./cross.patch
+  ++ lib.optional (crossCompiling && stdenv.hostPlatform.isCygwin) ./fix-cygwin-cross.patch;
 
   libc = if stdenv.cc.libc or null != null then stdenv.cc.libc else "/usr";
   libcInc = lib.getDev libc;
@@ -137,10 +138,18 @@ stdenv.mkDerivation (
           ''
       )
       +
-      # Perl's build system uses the src variable, and its value may end up in
-      # the output in some cases (when cross-compiling)
-      ''
-        unset src
+        # Perl's build system uses the src variable, and its value may end up in
+        # the output in some cases (when cross-compiling)
+        ''
+          unset src
+        ''
+      + lib.optionalString stdenv.buildPlatform.isCygwin ''
+        substituteInPlace hints/cygwin.sh \
+          --replace-fail "PATH='.:/usr/bin/'" ""
+        substituteInPlace cpan/Win32/Makefile.PL haiku/Haiku/Makefile.PL \
+          --replace-fail '/lib/w32api' '${lib.getLib stdenv.cc.libc.w32api}${
+            stdenv.cc.libc.w32api.libdir or "/lib/w32api"
+          }'
       '';
 
     # Build a thread-safe Perl with a dynamic libperl.so.  We need the
@@ -158,6 +167,24 @@ stdenv.mkDerivation (
             # https://github.com/arsv/perl-cross/issues/158
             "-Dd_gnulibc=define"
           ]
+          # these currently can't be configured automatically on non-elf systems
+          # other archs will need verification
+          ++ lib.optional (stdenv.hostPlatform.isCygwin && stdenv.hostPlatform.isx86_64) [
+            "-Dcharsize=1"
+            "-Dshortsize=2"
+            "-Dintsize=4"
+            "-Dlongsize=8"
+            "-Ddoublesize=8"
+            "-Dptrsize=8"
+            "-Dlongdblsize=16"
+            "-Dlonglongsize=8"
+            "-Dsizesize=8"
+            "-Dfpossize=8"
+            "-Dlseeksize=8"
+            "-Duidsize=4"
+            "-Dgidsize=4"
+            "-Dtimesize=8"
+          ]
         else
           (
             [
@@ -267,6 +294,18 @@ stdenv.mkDerivation (
     # Default perl does not support --host= & co.
     configurePlatforms = [ ];
 
+    allowedImpureDLLs = [
+      "ADVAPI32.dll"
+      "NETAPI32.dll"
+      "SHELL32.dll"
+      "USER32.dll"
+      "USERENV.dll"
+      "VERSION.dll"
+      "WINHTTP.dll"
+      "ntdll.dll"
+      "ole32.dll"
+    ];
+
     setupHook = ./setup-hook.sh;
 
     env = {
@@ -401,4 +440,9 @@ stdenv.mkDerivation (
     # TODO merge setup hooks
     setupHook = ./setup-hook-cross.sh;
   }
+  // lib.optionalAttrs (stdenv.hostPlatform.isCygwin) {
+    # in cygwin we need PATH and HOST_PATH set up for these dependencies
+    buildInputs = [ zlib ];
+    nativeBuildInputs = lib.optional (!crossCompiling && enableCrypt) libxcrypt;
+  }
 )
diff --git a/pkgs/development/interpreters/python/cpython/default.nix b/pkgs/development/interpreters/python/cpython/default.nix
index 13ede05bf2b72..678a6bf4188c1 100644
--- a/pkgs/development/interpreters/python/cpython/default.nix
+++ b/pkgs/development/interpreters/python/cpython/default.nix
@@ -95,6 +95,7 @@
 
   # tests
   testers,
+  runCommand,
 
   # allow pythonMinimal to prevent accidental dependencies it doesn't want
   # Having this as an option is useful to allow overriding, eg. adding things to
@@ -211,7 +212,8 @@ let
   ++
     optionals
       (
-        (!stdenv.hostPlatform.isDarwin && !withMinimalDeps)
+        # on cygwin this is needed for fix-cygwin-build.patch
+        (!stdenv.hostPlatform.isDarwin && !withMinimalDeps || stdenv.hostPlatform.isCygwin)
         || (stdenv.hostPlatform != stdenv.buildPlatform && stdenv.hostPlatform.isFreeBSD)
       )
       [
@@ -435,7 +437,8 @@ stdenv.mkDerivation (finalAttrs: {
       "mingw-python3_setenv.patch"
       "mingw-python3_win-modules.patch"
     ])
-  );
+  )
+  ++ optionals stdenv.hostPlatform.isCygwin [ ./fix-cygwin-build.patch ];
 
   postPatch =
     optionalString (!stdenv.hostPlatform.isWindows) ''
@@ -728,6 +731,9 @@ stdenv.mkDerivation (finalAttrs: {
 
       echo linking DLLs for python’s compiled librairies
       linkDLLsInfolder $out/lib/python*/lib-dynload/
+    ''
+    + optionalString stdenv.hostPlatform.isCygwin ''
+      linkDLLsDir="$out"/bin linkDLLs "$out"/lib/python*/lib-dynload/*.cpython-*.dll
     '';
 
   preFixup = lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) ''
@@ -737,34 +743,40 @@ stdenv.mkDerivation (finalAttrs: {
 
   # Add CPython specific setup-hook that configures distutils.sysconfig to
   # always load sysconfigdata from host Python.
-  postFixup = lib.optionalString (!stdenv.hostPlatform.isDarwin) ''
-    # https://github.com/python/cpython/blob/e488e300f5c01289c10906c2e53a8e43d6de32d8/configure.ac#L78
-    sysconfigdataName="$(make --eval $'print-sysconfigdata-name:
-    \t@echo _sysconfigdata_$(ABIFLAGS)_$(MACHDEP)_$(MULTIARCH) ' print-sysconfigdata-name)"
-
-    # The CPython interpreter contains a _sysconfigdata_<platform specific suffix>
-    # module that is imported by the sysconfig and distutils.sysconfig modules.
-    # The sysconfigdata module is generated at build time and contains settings
-    # required for building Python extension modules, such as include paths and
-    # other compiler flags. By default, the sysconfigdata module is loaded from
-    # the currently running interpreter (ie. the build platform interpreter), but
-    # when cross-compiling we want to load it from the host platform interpreter.
-    # This can be done using the _PYTHON_SYSCONFIGDATA_NAME environment variable.
-    # The _PYTHON_HOST_PLATFORM variable also needs to be set to get the correct
-    # platform suffix on extension modules. The correct values for these variables
-    # are not documented, and must be derived from the configure script (see links
-    # below).
-    cat <<EOF >> "$out/nix-support/setup-hook"
-    sysconfigdataHook() {
-      if [ "\$1" = '$out' ]; then
-        export _PYTHON_HOST_PLATFORM='${pythonHostPlatform}'
-        export _PYTHON_SYSCONFIGDATA_NAME='$sysconfigdataName'
-      fi
-    }
-
-    addEnvHooks "\$hostOffset" sysconfigdataHook
-    EOF
-  '';
+  postFixup =
+    lib.optionalString (!stdenv.hostPlatform.isDarwin) ''
+      # https://github.com/python/cpython/blob/e488e300f5c01289c10906c2e53a8e43d6de32d8/configure.ac#L78
+      sysconfigdataName="$(make --eval $'print-sysconfigdata-name:
+      \t@echo _sysconfigdata_$(ABIFLAGS)_$(MACHDEP)_$(MULTIARCH) ' print-sysconfigdata-name)"
+
+      # The CPython interpreter contains a _sysconfigdata_<platform specific suffix>
+      # module that is imported by the sysconfig and distutils.sysconfig modules.
+      # The sysconfigdata module is generated at build time and contains settings
+      # required for building Python extension modules, such as include paths and
+      # other compiler flags. By default, the sysconfigdata module is loaded from
+      # the currently running interpreter (ie. the build platform interpreter), but
+      # when cross-compiling we want to load it from the host platform interpreter.
+      # This can be done using the _PYTHON_SYSCONFIGDATA_NAME environment variable.
+      # The _PYTHON_HOST_PLATFORM variable also needs to be set to get the correct
+      # platform suffix on extension modules. The correct values for these variables
+      # are not documented, and must be derived from the configure script (see links
+      # below).
+      cat <<EOF >> "$out/nix-support/setup-hook"
+      sysconfigdataHook() {
+        if [ "\$1" = '$out' ]; then
+          export _PYTHON_HOST_PLATFORM='${pythonHostPlatform}'
+          export _PYTHON_SYSCONFIGDATA_NAME='$sysconfigdataName'
+        fi
+      }
+
+      addEnvHooks "\$hostOffset" sysconfigdataHook
+      EOF
+    ''
+    # borrowed from cygwin python39.cygport
+    # this is needed for the flags in python3.pc to work
+    + optionalString stdenv.hostPlatform.isCygwin ''
+      cp libpython*.dll.a "$out"/lib
+    '';
 
   # Enforce that we don't have references to the OpenSSL -dev package, which we
   # explicitly specify in our configure flags above.
@@ -821,9 +833,24 @@ stdenv.mkDerivation (finalAttrs: {
       ];
     };
 
-    tests = passthru.tests // {
-      pkg-config = testers.testMetaPkgConfig finalAttrs.finalPackage;
-    };
+    tests =
+      passthru.tests
+      // {
+        pkg-config = testers.testMetaPkgConfig finalAttrs.finalPackage;
+      }
+      // (
+        let
+          testPython =
+            name: script:
+            runCommand "python-test-${name}" {
+              inherit script;
+            } ''"${lib.getExe finalAttrs.finalPackage}" -c "$script" > "$out"'';
+        in
+        {
+          sax = testPython "sax" "import xml.sax;xml.sax.make_parser()";
+          semaphore = testPython "semaphore" "from _multiprocessing import SemLock";
+        }
+      );
   };
 
   enableParallelBuilding = true;
@@ -852,7 +879,11 @@ stdenv.mkDerivation (finalAttrs: {
     license = lib.licenses.psfl;
     pkgConfigModules = [ "python3" ];
     platforms =
-      lib.platforms.linux ++ lib.platforms.darwin ++ lib.platforms.windows ++ lib.platforms.freebsd;
+      lib.platforms.linux
+      ++ lib.platforms.darwin
+      ++ lib.platforms.windows
+      ++ lib.platforms.cygwin
+      ++ lib.platforms.freebsd;
     mainProgram = executable;
     teams = [ lib.teams.python ];
     # static build on x86_64-darwin/aarch64-darwin breaks with:
diff --git a/pkgs/development/interpreters/python/cpython/fix-cygwin-build.patch b/pkgs/development/interpreters/python/cpython/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..117b6807a33e6
--- /dev/null
+++ b/pkgs/development/interpreters/python/cpython/fix-cygwin-build.patch
@@ -0,0 +1,145 @@
+diff --git a/Makefile.pre.in b/Makefile.pre.in
+index a7dc9709d62..c37f735b676 100644
+--- a/Makefile.pre.in
++++ b/Makefile.pre.in
+@@ -43,6 +43,7 @@ SOABI=		@SOABI@
+ ABIFLAGS=	@ABIFLAGS@
+ ABI_THREAD=	@ABI_THREAD@
+ LDVERSION=	@LDVERSION@
++BLIBPYTHON=@BLIBPYTHON@
+ LIBPYTHON=@LIBPYTHON@
+ GITVERSION=	@GITVERSION@
+ GITTAG=		@GITTAG@
+diff --git a/Misc/python.pc.in b/Misc/python.pc.in
+index 027dba38585..6414141e15e 100644
+--- a/Misc/python.pc.in
++++ b/Misc/python.pc.in
+@@ -9,5 +9,5 @@ Description: Build a C extension for Python
+ Requires:
+ Version: @VERSION@
+ Libs.private: @LIBS@
+-Libs: -L${libdir} @LIBPYTHON@
++Libs: @LIBPYTHON@
+ Cflags: -I${includedir}/python@VERSION@@ABIFLAGS@
+diff --git a/Modules/makesetup b/Modules/makesetup
+index 8bb971b152a..cedc9ce6471 100755
+--- a/Modules/makesetup
++++ b/Modules/makesetup
+@@ -274,7 +274,7 @@ sed -e 's/[ 	]*#.*//' -e '/^[ 	]*$/d' |
+ 				;;
+ 			esac
+ 			rule="$file: $objs"
+-			rule="$rule; \$(BLDSHARED) $objs $libs \$(LIBPYTHON) -o $file"
++			rule="$rule; \$(BLDSHARED) $objs $libs \$(BLIBPYTHON) -o $file"
+ 			echo "$rule" >>$rulesf
+ 		done
+ 	done
+diff --git a/Modules/timemodule.c b/Modules/timemodule.c
+index 49626d32fd3..fd741628894 100644
+--- a/Modules/timemodule.c
++++ b/Modules/timemodule.c
+@@ -187,7 +187,7 @@ time_clockid_converter(PyObject *obj, clockid_t *p)
+ {
+ #ifdef _AIX
+     long long clk_id = PyLong_AsLongLong(obj);
+-#elif defined(__DragonFly__)
++#elif defined(__DragonFly__) || defined(__CYGWIN__)
+     long clk_id = PyLong_AsLong(obj);
+ #else
+     int clk_id = PyLong_AsInt(obj);
+diff --git a/Python/dynload_shlib.c b/Python/dynload_shlib.c
+index 5a37a83805b..3b6dec254ed 100644
+--- a/Python/dynload_shlib.c
++++ b/Python/dynload_shlib.c
+@@ -36,6 +36,10 @@
+ 
+ const char *_PyImport_DynLoadFiletab[] = {
+ #ifdef __CYGWIN__
++    "." SOABI ".dll",
++#ifdef ALT_SOABI
++    "." ALT_SOABI ".dll",
++#endif
+     ".dll",
+ #else  /* !__CYGWIN__ */
+     "." SOABI ".so",
+diff --git a/configure.ac b/configure.ac
+index 597a44b331a..e271a9bfdf0 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -325,7 +325,7 @@ then
+ 		ac_sys_system=Linux
+ 		;;
+ 	*-*-cygwin*)
+-		ac_sys_system=Cygwin
++		ac_sys_system=CYGWIN
+ 		;;
+ 	*-apple-ios*)
+ 		ac_sys_system=iOS
+@@ -3540,8 +3540,8 @@ then
+ 			dnl not implemented yet
+ 		]);;
+ 	CYGWIN*)
+-		LDSHARED="gcc -shared -Wl,--enable-auto-image-base"
+-		LDCXXSHARED="g++ -shared -Wl,--enable-auto-image-base";;
++		LDSHARED='$(CC) -shared -Wl,--enable-auto-image-base'
++		LDCXXSHARED='$(CXX) -shared -Wl,--enable-auto-image-base';;
+ 	*)	LDSHARED="ld";;
+ 	esac
+ fi
+@@ -6307,26 +6307,6 @@ AC_MSG_CHECKING([LDVERSION])
+ LDVERSION='$(VERSION)$(ABIFLAGS)'
+ AC_MSG_RESULT([$LDVERSION])
+ 
+-# Configure the flags and dependencies used when compiling shared modules.
+-# Do not rename LIBPYTHON - it's accessed via sysconfig by package build
+-# systems (e.g. Meson) to decide whether to link extension modules against
+-# libpython.
+-AC_SUBST([MODULE_DEPS_SHARED])
+-AC_SUBST([LIBPYTHON])
+-MODULE_DEPS_SHARED='$(MODULE_DEPS_STATIC) $(EXPORTSYMS)'
+-LIBPYTHON=''
+-
+-# On Android and Cygwin the shared libraries must be linked with libpython.
+-if test "$PY_ENABLE_SHARED" = "1" && ( test -n "$ANDROID_API_LEVEL" || test "$MACHDEP" = "cygwin"); then
+-  MODULE_DEPS_SHARED="$MODULE_DEPS_SHARED \$(LDLIBRARY)"
+-  LIBPYTHON="\$(BLDLIBRARY)"
+-fi
+-
+-# On iOS the shared libraries must be linked with the Python framework
+-if test "$ac_sys_system" = "iOS"; then
+-  MODULE_DEPS_SHARED="$MODULE_DEPS_SHARED \$(PYTHONFRAMEWORKDIR)/\$(PYTHONFRAMEWORK)"
+-fi
+-
+ 
+ AC_SUBST([BINLIBDEST])
+ BINLIBDEST='$(LIBDIR)/python$(VERSION)$(ABI_THREAD)'
+@@ -6368,6 +6348,29 @@ else
+ fi
+ AC_SUBST([LIBPL])
+ 
++# Configure the flags and dependencies used when compiling shared modules.
++# Do not rename LIBPYTHON - it's accessed via sysconfig by package build
++# systems (e.g. Meson) to decide whether to link extension modules against
++# libpython.
++AC_SUBST([MODULE_DEPS_SHARED])
++AC_SUBST([BLIBPYTHON])
++AC_SUBST([LIBPYTHON])
++MODULE_DEPS_SHARED='$(MODULE_DEPS_STATIC) $(EXPORTSYMS)'
++BLIBPYTHON=''
++LIBPYTHON=''
++
++# On Android and Cygwin the shared libraries must be linked with libpython.
++if test "$PY_ENABLE_SHARED" = "1" && ( test -n "$ANDROID_API_LEVEL" || test "$MACHDEP" = "cygwin"); then
++MODULE_DEPS_SHARED="$MODULE_DEPS_SHARED \$(LDLIBRARY)"
++BLIBPYTHON="\$(BLDLIBRARY)"
++LIBPYTHON="-L\"$prefix\"/${PLATLIBDIR}/python${VERSION}${ABI_THREAD}/config-${VERSION}${ABIFLAGS}${PLATFORM_TRIPLET+-$PLATFORM_TRIPLET} -lpython${VERSION}${ABIFLAGS}"
++fi
++
++# On iOS the shared libraries must be linked with the Python framework
++if test "$ac_sys_system" = "iOS"; then
++  MODULE_DEPS_SHARED="$MODULE_DEPS_SHARED \$(PYTHONFRAMEWORKDIR)/\$(PYTHONFRAMEWORK)"
++fi
++
+ # Check for --with-wheel-pkg-dir=PATH
+ AC_SUBST([WHEEL_PKG_DIR])
+ WHEEL_PKG_DIR=""
diff --git a/pkgs/development/interpreters/tcl/fix-cygwin-build.patch b/pkgs/development/interpreters/tcl/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..2cee46424207a
--- /dev/null
+++ b/pkgs/development/interpreters/tcl/fix-cygwin-build.patch
@@ -0,0 +1,619 @@
+From 3b266a8b33a4b1090a7d87662b6d1e23187c96d3 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Wed, 8 Oct 2025 15:37:12 -0300
+Subject: [PATCH] fix cygwin build
+
+---
+ generic/tcl.h             |  2 +-
+ generic/tclCmdAH.c        |  2 +-
+ generic/tclDecls.h        |  2 +-
+ generic/tclFCmd.c         |  2 +-
+ generic/tclIOSock.c       |  2 +-
+ generic/tclIntPlatDecls.h | 12 ++++++------
+ generic/tclPanic.c        |  8 ++++----
+ generic/tclPlatDecls.h    |  8 ++++----
+ generic/tclStubInit.c     | 10 +++++-----
+ tools/genStubs.tcl        |  9 ---------
+ unix/Makefile.in          |  5 +----
+ unix/tcl.m4               | 15 ++++++++++++++-
+ unix/tclUnixFCmd.c        | 37 +++++--------------------------------
+ unix/tclUnixFile.c        |  4 ++--
+ unix/tclUnixInit.c        |  6 +++---
+ unix/tclUnixNotfy.c       | 22 +++++++++++-----------
+ unix/tclUnixPort.h        |  2 +-
+ 17 files changed, 61 insertions(+), 87 deletions(-)
+
+diff --git a/generic/tcl.h b/generic/tcl.h
+index fc772d5b3c..539f7ce300 100644
+--- a/generic/tcl.h
++++ b/generic/tcl.h
+@@ -462,7 +462,7 @@ typedef unsigned TCL_WIDE_INT_TYPE	Tcl_WideUInt;
+ #   else
+ 	typedef struct _stat32i64 Tcl_StatBuf;
+ #   endif /* _MSC_VER < 1400 */
+-#elif defined(__CYGWIN__)
++#elif 0
+     typedef struct {
+ 	unsigned st_dev;
+ 	unsigned short st_ino;
+diff --git a/generic/tclCmdAH.c b/generic/tclCmdAH.c
+index adbe9a699d..f0933d12a2 100644
+--- a/generic/tclCmdAH.c
++++ b/generic/tclCmdAH.c
+@@ -1788,7 +1788,7 @@ FileAttrIsOwnedCmd(
+     int objc,
+     Tcl_Obj *const objv[])
+ {
+-#ifdef __CYGWIN__
++#if 0
+ #define geteuid() (short)(geteuid)()
+ #endif
+ #if !defined(_WIN32)
+diff --git a/generic/tclDecls.h b/generic/tclDecls.h
+index 27b4edc4cd..925050ddf1 100644
+--- a/generic/tclDecls.h
++++ b/generic/tclDecls.h
+@@ -4055,7 +4055,7 @@ extern const TclStubs *tclStubsPtr;
+ 		    *(t) = _t.now; \
+ 		} while (0)
+ #   endif
+-#   if defined(__CYGWIN__) && defined(TCL_WIDE_INT_IS_LONG)
++#   if 0
+ /* On Cygwin64, long is 64-bit while on Win64 long is 32-bit. Therefore
+  * we have to make sure that all stub entries on Cygwin64 follow the
+  * Win64 signature. Cygwin64 stubbed extensions cannot use those stub
+diff --git a/generic/tclFCmd.c b/generic/tclFCmd.c
+index e55088209c..c6b9e1881c 100644
+--- a/generic/tclFCmd.c
++++ b/generic/tclFCmd.c
+@@ -523,7 +523,7 @@ CopyRenameOneFile(
+ 	 * 16 bits and we get collisions. See bug #2015723.
+ 	 */
+ 
+-#if !defined(_WIN32) && !defined(__CYGWIN__)
++#if !defined(_WIN32)
+ 	if ((sourceStatBuf.st_ino != 0) && (targetStatBuf.st_ino != 0)) {
+ 	    if ((sourceStatBuf.st_ino == targetStatBuf.st_ino) &&
+ 		    (sourceStatBuf.st_dev == targetStatBuf.st_dev)) {
+diff --git a/generic/tclIOSock.c b/generic/tclIOSock.c
+index 64139609a5..b75fc18158 100644
+--- a/generic/tclIOSock.c
++++ b/generic/tclIOSock.c
+@@ -104,7 +104,7 @@ TclSockGetPort(
+  *----------------------------------------------------------------------
+  */
+ 
+-#if !defined(_WIN32) && !defined(__CYGWIN__)
++#if !defined(_WIN32)
+ #   define SOCKET int
+ #endif
+ 
+diff --git a/generic/tclIntPlatDecls.h b/generic/tclIntPlatDecls.h
+index 5bd4828441..5d8c43dce3 100644
+--- a/generic/tclIntPlatDecls.h
++++ b/generic/tclIntPlatDecls.h
+@@ -40,7 +40,7 @@ extern "C" {
+  * Exported function declarations:
+  */
+ 
+-#if !defined(_WIN32) && !defined(__CYGWIN__) && !defined(MAC_OSX_TCL) /* UNIX */
++#if !defined(_WIN32) && !defined(MAC_OSX_TCL) /* UNIX */
+ /* 0 */
+ EXTERN void		TclGetAndDetachPids(Tcl_Interp *interp,
+ 				Tcl_Channel chan);
+@@ -116,7 +116,7 @@ EXTERN int		TclUnixOpenTemporaryFile(Tcl_Obj *dirObj,
+ 				Tcl_Obj *basenameObj, Tcl_Obj *extensionObj,
+ 				Tcl_Obj *resultingNameObj);
+ #endif /* UNIX */
+-#if defined(_WIN32) || defined(__CYGWIN__) /* WIN */
++#if defined(_WIN32) /* WIN */
+ /* 0 */
+ EXTERN void		TclWinConvertError(DWORD errCode);
+ /* 1 */
+@@ -272,7 +272,7 @@ typedef struct TclIntPlatStubs {
+     int magic;
+     void *hooks;
+ 
+-#if !defined(_WIN32) && !defined(__CYGWIN__) && !defined(MAC_OSX_TCL) /* UNIX */
++#if !defined(_WIN32) && !defined(MAC_OSX_TCL) /* UNIX */
+     void (*tclGetAndDetachPids) (Tcl_Interp *interp, Tcl_Channel chan); /* 0 */
+     int (*tclpCloseFile) (TclFile file); /* 1 */
+     Tcl_Channel (*tclpCreateCommandChannel) (TclFile readFile, TclFile writeFile, TclFile errorFile, int numPids, Tcl_Pid *pidPtr); /* 2 */
+@@ -305,7 +305,7 @@ typedef struct TclIntPlatStubs {
+     int (*tclWinCPUID) (unsigned int index, unsigned int *regs); /* 29 */
+     int (*tclUnixOpenTemporaryFile) (Tcl_Obj *dirObj, Tcl_Obj *basenameObj, Tcl_Obj *extensionObj, Tcl_Obj *resultingNameObj); /* 30 */
+ #endif /* UNIX */
+-#if defined(_WIN32) || defined(__CYGWIN__) /* WIN */
++#if defined(_WIN32) /* WIN */
+     void (*tclWinConvertError) (DWORD errCode); /* 0 */
+     void (*tclWinConvertWSAError) (DWORD errCode); /* 1 */
+     struct servent * (*tclWinGetServByName) (const char *nm, const char *proto); /* 2 */
+@@ -385,7 +385,7 @@ extern const TclIntPlatStubs *tclIntPlatStubsPtr;
+  * Inline function declarations:
+  */
+ 
+-#if !defined(_WIN32) && !defined(__CYGWIN__) && !defined(MAC_OSX_TCL) /* UNIX */
++#if !defined(_WIN32) && !defined(MAC_OSX_TCL) /* UNIX */
+ #define TclGetAndDetachPids \
+ 	(tclIntPlatStubsPtr->tclGetAndDetachPids) /* 0 */
+ #define TclpCloseFile \
+@@ -441,7 +441,7 @@ extern const TclIntPlatStubs *tclIntPlatStubsPtr;
+ #define TclUnixOpenTemporaryFile \
+ 	(tclIntPlatStubsPtr->tclUnixOpenTemporaryFile) /* 30 */
+ #endif /* UNIX */
+-#if defined(_WIN32) || defined(__CYGWIN__) /* WIN */
++#if defined(_WIN32) /* WIN */
+ #define TclWinConvertError \
+ 	(tclIntPlatStubsPtr->tclWinConvertError) /* 0 */
+ #define TclWinConvertWSAError \
+diff --git a/generic/tclPanic.c b/generic/tclPanic.c
+index 56c8fbcbae..aea7121cad 100644
+--- a/generic/tclPanic.c
++++ b/generic/tclPanic.c
+@@ -14,7 +14,7 @@
+  */
+ 
+ #include "tclInt.h"
+-#if defined(_WIN32) || defined(__CYGWIN__)
++#if defined(_WIN32)
+     MODULE_SCOPE TCL_NORETURN void tclWinDebugPanic(const char *format, ...);
+ #endif
+ 
+@@ -23,7 +23,7 @@
+  * procedure.
+  */
+ 
+-#if defined(__CYGWIN__)
++#if 0
+ static Tcl_PanicProc *panicProc = tclWinDebugPanic;
+ #else
+ static Tcl_PanicProc *panicProc = NULL;
+@@ -52,7 +52,7 @@ Tcl_SetPanicProc(
+ #if defined(_WIN32)
+     /* tclWinDebugPanic only installs if there is no panicProc yet. */
+     if ((proc != tclWinDebugPanic) || (panicProc == NULL))
+-#elif defined(__CYGWIN__)
++#elif 0
+     if (proc == NULL)
+ 	panicProc = tclWinDebugPanic;
+     else
+@@ -107,7 +107,7 @@ Tcl_PanicVA(
+ 	fprintf(stderr, "\n");
+ 	fflush(stderr);
+     }
+-#if defined(_WIN32) || defined(__CYGWIN__)
++#if defined(_WIN32)
+ #if defined(__GNUC__)
+     __builtin_trap();
+ #elif defined(_WIN64)
+diff --git a/generic/tclPlatDecls.h b/generic/tclPlatDecls.h
+index 46181a1d61..b11e851dbf 100644
+--- a/generic/tclPlatDecls.h
++++ b/generic/tclPlatDecls.h
+@@ -31,7 +31,7 @@
+  * TCHAR is needed here for win32, so if it is not defined yet do it here.
+  * This way, we don't need to include <tchar.h> just for one define.
+  */
+-#if (defined(_WIN32) || defined(__CYGWIN__)) && !defined(_TCHAR_DEFINED)
++#if defined(_WIN32) && !defined(_TCHAR_DEFINED)
+ #   if defined(_UNICODE)
+ 	typedef wchar_t TCHAR;
+ #   else
+@@ -50,7 +50,7 @@ extern "C" {
+  * Exported function declarations:
+  */
+ 
+-#if defined(_WIN32) || defined(__CYGWIN__) /* WIN */
++#if defined(_WIN32) /* WIN */
+ /* 0 */
+ EXTERN TCHAR *		Tcl_WinUtfToTChar(const char *str, int len,
+ 				Tcl_DString *dsPtr);
+@@ -81,7 +81,7 @@ typedef struct TclPlatStubs {
+     int magic;
+     void *hooks;
+ 
+-#if defined(_WIN32) || defined(__CYGWIN__) /* WIN */
++#if defined(_WIN32) /* WIN */
+     TCHAR * (*tcl_WinUtfToTChar) (const char *str, int len, Tcl_DString *dsPtr); /* 0 */
+     char * (*tcl_WinTCharToUtf) (const TCHAR *str, int len, Tcl_DString *dsPtr); /* 1 */
+     void (*reserved2)(void);
+@@ -106,7 +106,7 @@ extern const TclPlatStubs *tclPlatStubsPtr;
+  * Inline function declarations:
+  */
+ 
+-#if defined(_WIN32) || defined(__CYGWIN__) /* WIN */
++#if defined(_WIN32) /* WIN */
+ #define Tcl_WinUtfToTChar \
+ 	(tclPlatStubsPtr->tcl_WinUtfToTChar) /* 0 */
+ #define Tcl_WinTCharToUtf \
+diff --git a/generic/tclStubInit.c b/generic/tclStubInit.c
+index cd6d46b2dd..f0966d9b7f 100644
+--- a/generic/tclStubInit.c
++++ b/generic/tclStubInit.c
+@@ -139,7 +139,7 @@ static const char *TclGetStartupScriptFileName(void)
+     return Tcl_GetString(path);
+ }
+ 
+-#if defined(_WIN32) || defined(__CYGWIN__)
++#if defined(_WIN32)
+ #undef TclWinNToHS
+ #define TclWinNToHS winNToHS
+ static unsigned short TclWinNToHS(unsigned short ns) {
+@@ -169,7 +169,7 @@ TclWinConvertError_(unsigned errCode) {
+ #   define TclUnixOpenTemporaryFile 0
+ #   define TclpReaddir 0
+ #   define TclpIsAtty 0
+-#elif defined(__CYGWIN__)
++#elif 0
+ #   define TclpIsAtty isatty
+ #   define TclWinSetInterfaces (void (*) (int))(void *)doNothing
+ #   define TclWinAddProcess (void (*) (void *, unsigned int))(void *)doNothing
+@@ -764,7 +764,7 @@ static const TclIntStubs tclIntStubs = {
+ static const TclIntPlatStubs tclIntPlatStubs = {
+     TCL_STUB_MAGIC,
+     0,
+-#if !defined(_WIN32) && !defined(__CYGWIN__) && !defined(MAC_OSX_TCL) /* UNIX */
++#if !defined(_WIN32) && !defined(MAC_OSX_TCL) /* UNIX */
+     TclGetAndDetachPids, /* 0 */
+     TclpCloseFile, /* 1 */
+     TclpCreateCommandChannel, /* 2 */
+@@ -797,7 +797,7 @@ static const TclIntPlatStubs tclIntPlatStubs = {
+     TclWinCPUID, /* 29 */
+     TclUnixOpenTemporaryFile, /* 30 */
+ #endif /* UNIX */
+-#if defined(_WIN32) || defined(__CYGWIN__) /* WIN */
++#if defined(_WIN32) /* WIN */
+     TclWinConvertError, /* 0 */
+     TclWinConvertWSAError, /* 1 */
+     TclWinGetServByName, /* 2 */
+@@ -868,7 +868,7 @@ static const TclIntPlatStubs tclIntPlatStubs = {
+ static const TclPlatStubs tclPlatStubs = {
+     TCL_STUB_MAGIC,
+     0,
+-#if defined(_WIN32) || defined(__CYGWIN__) /* WIN */
++#if defined(_WIN32) /* WIN */
+     Tcl_WinUtfToTChar, /* 0 */
+     Tcl_WinTCharToUtf, /* 1 */
+     0, /* 2 */
+diff --git a/tools/genStubs.tcl b/tools/genStubs.tcl
+index 3c9964556f..416a89e14a 100644
+--- a/tools/genStubs.tcl
++++ b/tools/genStubs.tcl
+@@ -299,9 +299,6 @@ proc genStubs::addPlatformGuard {plat iftxt {eltxt {}} {withCygwin 0}} {
+     switch $plat {
+ 	win {
+ 	    append text "#if defined(_WIN32)"
+-	    if {$withCygwin} {
+-		append text " || defined(__CYGWIN__)"
+-	    }
+ 	    append text " /* WIN */\n${iftxt}"
+ 	    if {$eltxt ne ""} {
+ 		append text "#else /* WIN */\n${eltxt}"
+@@ -310,9 +307,6 @@ proc genStubs::addPlatformGuard {plat iftxt {eltxt {}} {withCygwin 0}} {
+ 	}
+ 	unix {
+ 	    append text "#if !defined(_WIN32)"
+-	    if {$withCygwin} {
+-		append text " && !defined(__CYGWIN__)"
+-	    }
+ 	    append text " && !defined(MAC_OSX_TCL)\
+ 		    /* UNIX */\n${iftxt}"
+ 	    if {$eltxt ne ""} {
+@@ -336,9 +330,6 @@ proc genStubs::addPlatformGuard {plat iftxt {eltxt {}} {withCygwin 0}} {
+ 	}
+ 	x11 {
+ 	    append text "#if !(defined(_WIN32)"
+-	    if {$withCygwin} {
+-		append text " || defined(__CYGWIN__)"
+-	    }
+ 	    append text " || defined(MAC_OSX_TK))\
+ 		    /* X11 */\n${iftxt}"
+ 	    if {$eltxt ne ""} {
+diff --git a/unix/Makefile.in b/unix/Makefile.in
+index bc743b3892..dc80d61c2f 100644
+--- a/unix/Makefile.in
++++ b/unix/Makefile.in
+@@ -358,7 +358,7 @@ NOTIFY_OBJS = tclUnixNotfy.o
+ 
+ MAC_OSX_OBJS = tclMacOSXBundle.o tclMacOSXFCmd.o tclMacOSXNotify.o
+ 
+-CYGWIN_OBJS = tclWinError.o
++CYGWIN_OBJS =
+ 
+ DTRACE_OBJ = tclDTrace.o
+ 
+@@ -637,9 +637,6 @@ ${LIB_FILE}: ${STUB_LIB_FILE} ${OBJS}
+ 	@MAKE_LIB@
+ 
+ ${STUB_LIB_FILE}: ${STUB_LIB_OBJS}
+-	@if test "x${LIB_FILE}" = "xlibtcl${MAJOR_VERSION}.${MINOR_VERSION}.dll"; then \
+-	    (cd ${TOP_DIR}/win; ${MAKE} winextensions); \
+-	fi
+ 	rm -f $@
+ 	@MAKE_STUB_LIB@
+ 
+diff --git a/unix/tcl.m4 b/unix/tcl.m4
+index 7f5464e651..febae32214 100644
+--- a/unix/tcl.m4
++++ b/unix/tcl.m4
+@@ -1183,7 +1183,20 @@ AC_DEFUN([SC_CONFIG_CFLAGS], [
+ 	    CC_SEARCH_FLAGS=""
+ 	    LD_SEARCH_FLAGS=""
+ 	    ;;
+-	CYGWIN_*|MINGW32_*|MSYS_*)
++	CYGWIN_*)
++	    SHLIB_CFLAGS=""
++	    SHLIB_LD='${CC} -shared'
++	    SHLIB_SUFFIX=".dll"
++	    DL_OBJS="tclLoadDl.o"
++	    DL_LIBS="-ldl"
++	    CC_SEARCH_FLAGS=""
++	    LD_SEARCH_FLAGS=""
++	    TCL_NEEDS_EXP_FILE=1
++	    TCL_EXPORT_FILE_SUFFIX='${VERSION}\$\{DBGX\}.dll.a'
++	    SHLIB_LD_LIBS="${SHLIB_LD_LIBS} -Wl,--out-implib,\$[@].a"
++	    do64bit_ok=yes
++	    ;;
++	MINGW32_*|MSYS_*)
+ 	    SHLIB_CFLAGS="-fno-common"
+ 	    SHLIB_LD='${CC} -shared'
+ 	    SHLIB_SUFFIX=".dll"
+diff --git a/unix/tclUnixFCmd.c b/unix/tclUnixFCmd.c
+index 3d44124e8b..40e3a8a666 100644
+--- a/unix/tclUnixFCmd.c
++++ b/unix/tclUnixFCmd.c
+@@ -91,7 +91,7 @@ static int		SetPermissionsAttribute(Tcl_Interp *interp,
+ 			    Tcl_Obj *attributePtr);
+ static int		GetModeFromPermString(Tcl_Interp *interp,
+ 			    const char *modeStringPtr, mode_t *modePtr);
+-#if defined(HAVE_CHFLAGS) && defined(UF_IMMUTABLE) || defined(__CYGWIN__)
++#if defined(HAVE_CHFLAGS) && defined(UF_IMMUTABLE)
+ static int		GetUnixFileAttributes(Tcl_Interp *interp, int objIndex,
+ 			    Tcl_Obj *fileName, Tcl_Obj **attributePtrPtr);
+ static int		SetUnixFileAttributes(Tcl_Interp *interp, int objIndex,
+@@ -124,20 +124,11 @@ extern const char *const tclpFileAttrStrings[];
+ 
+ #else /* !DJGPP */
+ enum {
+-#if defined(__CYGWIN__)
+-    UNIX_ARCHIVE_ATTRIBUTE,
+-#endif
+     UNIX_GROUP_ATTRIBUTE,
+-#if defined(__CYGWIN__)
+-    UNIX_HIDDEN_ATTRIBUTE,
+-#endif
+     UNIX_OWNER_ATTRIBUTE, UNIX_PERMISSIONS_ATTRIBUTE,
+-#if defined(HAVE_CHFLAGS) && defined(UF_IMMUTABLE) || defined(__CYGWIN__)
++#if defined(HAVE_CHFLAGS) && defined(UF_IMMUTABLE)
+     UNIX_READONLY_ATTRIBUTE,
+ #endif
+-#if defined(__CYGWIN__)
+-    UNIX_SYSTEM_ATTRIBUTE,
+-#endif
+ #ifdef MAC_OSX_TCL
+     MACOSX_CREATOR_ATTRIBUTE, MACOSX_TYPE_ATTRIBUTE, MACOSX_HIDDEN_ATTRIBUTE,
+     MACOSX_RSRCLENGTH_ATTRIBUTE,
+@@ -147,20 +138,11 @@ enum {
+ 
+ MODULE_SCOPE const char *const tclpFileAttrStrings[];
+ const char *const tclpFileAttrStrings[] = {
+-#if defined(__CYGWIN__)
+-    "-archive",
+-#endif
+     "-group",
+-#if defined(__CYGWIN__)
+-    "-hidden",
+-#endif
+     "-owner", "-permissions",
+-#if defined(HAVE_CHFLAGS) && defined(UF_IMMUTABLE) || defined(__CYGWIN__)
++#if defined(HAVE_CHFLAGS) && defined(UF_IMMUTABLE)
+     "-readonly",
+ #endif
+-#if defined(__CYGWIN__)
+-    "-system",
+-#endif
+ #ifdef MAC_OSX_TCL
+     "-creator", "-type", "-hidden", "-rsrclength",
+ #endif
+@@ -169,19 +151,10 @@ const char *const tclpFileAttrStrings[] = {
+ 
+ MODULE_SCOPE const TclFileAttrProcs tclpFileAttrProcs[];
+ const TclFileAttrProcs tclpFileAttrProcs[] = {
+-#if defined(__CYGWIN__)
+-    {GetUnixFileAttributes, SetUnixFileAttributes},
+-#endif
+     {GetGroupAttribute, SetGroupAttribute},
+-#if defined(__CYGWIN__)
+-    {GetUnixFileAttributes, SetUnixFileAttributes},
+-#endif
+     {GetOwnerAttribute, SetOwnerAttribute},
+     {GetPermissionsAttribute, SetPermissionsAttribute},
+-#if defined(HAVE_CHFLAGS) && defined(UF_IMMUTABLE) || defined(__CYGWIN__)
+-    {GetUnixFileAttributes, SetUnixFileAttributes},
+-#endif
+-#if defined(__CYGWIN__)
++#if defined(HAVE_CHFLAGS) && defined(UF_IMMUTABLE)
+     {GetUnixFileAttributes, SetUnixFileAttributes},
+ #endif
+ #ifdef MAC_OSX_TCL
+@@ -2273,7 +2246,7 @@ DefaultTempDir(void)
+     return TCL_TEMPORARY_FILE_DIRECTORY;
+ }
+ 
+-#if defined(__CYGWIN__)
++#if 0
+ 
+ static void
+ StatError(
+diff --git a/unix/tclUnixFile.c b/unix/tclUnixFile.c
+index 9769b1338f..530b40a556 100644
+--- a/unix/tclUnixFile.c
++++ b/unix/tclUnixFile.c
+@@ -39,7 +39,7 @@ TclpFindExecutable(
+     const char *argv0)		/* The value of the application's argv[0]
+ 				 * (native). */
+ {
+-#ifdef __CYGWIN__
++#if 0
+     int length;
+     wchar_t buf[PATH_MAX] = L"";
+     char name[PATH_MAX * 3 + 1];
+@@ -1179,7 +1179,7 @@ TclpUtime(
+     return utime((const char *)Tcl_FSGetNativePath(pathPtr), tval);
+ }
+ 
+-#ifdef __CYGWIN__
++#if 0
+ 
+ int
+ TclOSstat(
+diff --git a/unix/tclUnixInit.c b/unix/tclUnixInit.c
+index c7b2efe811..ecd94fe7e0 100644
+--- a/unix/tclUnixInit.c
++++ b/unix/tclUnixInit.c
+@@ -32,7 +32,7 @@
+ #   endif
+ #endif
+ 
+-#ifdef __CYGWIN__
++#if 0
+ #ifdef __cplusplus
+ extern "C" {
+ #endif
+@@ -786,7 +786,7 @@ void
+ TclpSetVariables(
+     Tcl_Interp *interp)
+ {
+-#ifdef __CYGWIN__
++#if 0
+     SYSTEM_INFO sysInfo;
+     static OSVERSIONINFOW osInfo;
+     static int osInfoInitialized = 0;
+@@ -873,7 +873,7 @@ TclpSetVariables(
+ #endif
+ 
+     unameOK = 0;
+-#ifdef __CYGWIN__
++#if 0
+ 	unameOK = 1;
+     if (!osInfoInitialized) {
+ 	void *handle = GetModuleHandleW(L"NTDLL");
+diff --git a/unix/tclUnixNotfy.c b/unix/tclUnixNotfy.c
+index 0bee2f1cfa..087e58b0c5 100644
+--- a/unix/tclUnixNotfy.c
++++ b/unix/tclUnixNotfy.c
+@@ -93,7 +93,7 @@ typedef struct ThreadSpecificData {
+ 				 * from these pointers. You must hold the
+ 				 * notifierMutex lock before accessing these
+ 				 * fields. */
+-#ifdef __CYGWIN__
++#if 0
+     void *event;		/* Any other thread alerts a notifier that an
+ 				 * event is ready to be processed by sending
+ 				 * this event. */
+@@ -211,7 +211,7 @@ static int	FileHandlerEventProc(Tcl_Event *evPtr, int flags);
+  * Import of Windows API when building threaded with Cygwin.
+  */
+ 
+-#if defined(TCL_THREADS) && defined(__CYGWIN__)
++#if 0
+ typedef struct {
+     void *hwnd;			/* Messaging window. */
+     unsigned int *message;	/* Message payload. */
+@@ -339,7 +339,7 @@ Tcl_InitNotifier(void)
+ 	 * Initialize thread specific condition variable for this thread.
+ 	 */
+ 	if (tsdPtr->waitCVinitialized == 0) {
+-#ifdef __CYGWIN__
++#if 0
+ 	    WNDCLASSW clazz;
+ 
+ 	    clazz.style = 0;
+@@ -453,7 +453,7 @@ Tcl_FinalizeNotifier(
+ 	 * Clean up any synchronization objects in the thread local storage.
+ 	 */
+ 
+-#ifdef __CYGWIN__
++#if 0
+ 	DestroyWindow(tsdPtr->hwnd);
+ 	CloseHandle(tsdPtr->event);
+ #else /* __CYGWIN__ */
+@@ -499,7 +499,7 @@ Tcl_AlertNotifier(
+ 	pthread_mutex_lock(&notifierMutex);
+ 	tsdPtr->eventReady = 1;
+ 
+-#   ifdef __CYGWIN__
++#   if 0
+ 	PostMessageW(tsdPtr->hwnd, 1024, 0, 0);
+ #   else
+ 	pthread_cond_broadcast(&tsdPtr->waitCV);
+@@ -812,7 +812,7 @@ FileHandlerEventProc(
+     return 1;
+ }
+ 
+-#if defined(TCL_THREADS) && defined(__CYGWIN__)
++#if 0
+ 
+ static unsigned int __stdcall
+ NotifierProc(
+@@ -868,7 +868,7 @@ Tcl_WaitForEvent(
+ 	ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
+ #ifdef TCL_THREADS
+ 	int waitForFiles;
+-#   ifdef __CYGWIN__
++#   if 0
+ 	MSG msg;
+ #   endif /* __CYGWIN__ */
+ #else /* !TCL_THREADS */
+@@ -983,7 +983,7 @@ Tcl_WaitForEvent(
+ 	FD_ZERO(&tsdPtr->readyMasks.exception);
+ 
+ 	if (!tsdPtr->eventReady) {
+-#ifdef __CYGWIN__
++#if 0
+ 	    if (!PeekMessageW(&msg, NULL, 0, 0, 0)) {
+ 		unsigned int timeout;
+ 
+@@ -1014,7 +1014,7 @@ Tcl_WaitForEvent(
+ 	}
+ 	tsdPtr->eventReady = 0;
+ 
+-#ifdef __CYGWIN__
++#if 0
+ 	while (PeekMessageW(&msg, NULL, 0, 0, 0)) {
+ 	    /*
+ 	     * Retrieve and dispatch the message.
+@@ -1304,7 +1304,7 @@ NotifierThreadProc(
+ 		    tsdPtr->onList = 0;
+ 		    tsdPtr->pollState = 0;
+ 		}
+-#ifdef __CYGWIN__
++#if 0
+ 		PostMessageW(tsdPtr->hwnd, 1024, 0, 0);
+ #else /* __CYGWIN__ */
+ 		pthread_cond_broadcast(&tsdPtr->waitCV);
+@@ -1454,7 +1454,7 @@ AtForkChild(void)
+ 	     * The tsdPtr from before the fork is copied as well.  But since
+ 	     * we are paranoiac, we don't trust its condvar and reset it.
+ 	     */
+-#ifdef __CYGWIN__
++#if 0
+ 	    DestroyWindow(tsdPtr->hwnd);
+ 	    tsdPtr->hwnd = CreateWindowExW(NULL, NotfyClassName,
+ 		    NotfyClassName, 0, 0, 0, 0, 0, NULL, NULL,
+diff --git a/unix/tclUnixPort.h b/unix/tclUnixPort.h
+index 486fa23e38..63d8c51383 100644
+--- a/unix/tclUnixPort.h
++++ b/unix/tclUnixPort.h
+@@ -85,7 +85,7 @@ typedef off_t		Tcl_SeekOffset;
+ #   define TclOSopen		open
+ #endif
+ 
+-#ifdef __CYGWIN__
++#if 0
+ #ifdef __cplusplus
+ extern "C" {
+ #endif
+-- 
+2.50.1
+
diff --git a/pkgs/development/interpreters/tcl/generic.nix b/pkgs/development/interpreters/tcl/generic.nix
index 7ecc8250b9c24..260011227393e 100644
--- a/pkgs/development/interpreters/tcl/generic.nix
+++ b/pkgs/development/interpreters/tcl/generic.nix
@@ -7,6 +7,7 @@
   tzdata,
   zip,
   zlib,
+  fetchurl,
 
   # Version specific stuff
   release,
@@ -17,127 +18,140 @@
 }:
 
 let
-  baseInterp = stdenv.mkDerivation rec {
-    pname = "tcl";
-    inherit version src;
+  baseInterp = stdenv.mkDerivation (
+    rec {
+      pname = "tcl";
+      inherit version src;
 
-    outputs = [
-      "out"
-      "man"
-    ];
+      outputs = [
+        "out"
+        "man"
+      ];
 
-    setOutputFlags = false;
+      setOutputFlags = false;
 
-    postPatch = ''
-      substituteInPlace library/clock.tcl \
-        --replace "/usr/share/zoneinfo" "${tzdata}/share/zoneinfo" \
-        --replace "/usr/share/lib/zoneinfo" "" \
-        --replace "/usr/lib/zoneinfo" "" \
-        --replace "/usr/local/etc/zoneinfo" ""
-    ''
-    + extraPatch;
+      postPatch = ''
+        substituteInPlace library/clock.tcl \
+          --replace "/usr/share/zoneinfo" "${tzdata}/share/zoneinfo" \
+          --replace "/usr/share/lib/zoneinfo" "" \
+          --replace "/usr/lib/zoneinfo" "" \
+          --replace "/usr/local/etc/zoneinfo" ""
+      ''
+      + extraPatch;
 
-    nativeBuildInputs = lib.optionals (lib.versionAtLeast version "9.0") [
-      # Only used to detect the presence of zlib. Could be replaced with a stub.
-      zip
-    ];
+      nativeBuildInputs = lib.optionals (lib.versionAtLeast version "9.0") [
+        # Only used to detect the presence of zlib. Could be replaced with a stub.
+        zip
+      ];
 
-    buildInputs = lib.optionals (lib.versionAtLeast version "9.0") [
-      zlib
-    ];
+      buildInputs = lib.optionals (lib.versionAtLeast version "9.0") [
+        zlib
+      ];
 
-    preConfigure = ''
-      cd unix
-    '';
+      preConfigure = ''
+        cd unix
+      '';
 
-    # Note: pre-9.0 flags are temporarily interspersed to avoid a mass rebuild.
-    configureFlags =
-      lib.optionals (lib.versionOlder version "9.0") [
-        "--enable-threads"
-      ]
-      ++ [
-        # Note: using $out instead of $man to prevent a runtime dependency on $man.
-        "--mandir=${placeholder "out"}/share/man"
-      ]
-      ++ lib.optionals (lib.versionOlder version "9.0") [
-        "--enable-man-symlinks"
-        # Don't install tzdata because NixOS already has a more up-to-date copy.
-        "--with-tzdata=no"
-      ]
-      ++ lib.optionals (lib.versionOlder version "8.6") [
-        # configure check broke due to GCC 14
-        "ac_cv_header_stdc=yes"
-      ]
-      ++ lib.optionals (lib.versionAtLeast version "9.0") [
-        # By default, tcl libraries get zipped and embedded into libtcl*.so,
-        # which gets `zipfs mount`ed at runtime. This is fragile (for example
-        # stripping the .so removes the zip trailer), so we install them as
-        # traditional files.
-        # This might make tcl slower to start from slower storage on cold cache,
-        # however according to my benchmarks on fast storage and warm cache
-        # tcl built with --disable-zipfs actually starts in half the time.
-        "--disable-zipfs"
-      ]
-      ++ [
-        # During cross compilation, the tcl build system assumes that libc
-        # functions are broken if it cannot test if they are broken or not and
-        # then causes a link error on static platforms due to symbol conflict.
-        # These functions are *checks notes* strtoul and strstr. These are
-        # never broken on modern platforms!
-        "tcl_cv_strtod_unbroken=ok"
-        "tcl_cv_strtoul_unbroken=ok"
-        "tcl_cv_strstr_unbroken=ok"
-      ]
-      ++ lib.optional stdenv.hostPlatform.is64bit "--enable-64bit";
+      # Note: pre-9.0 flags are temporarily interspersed to avoid a mass rebuild.
+      configureFlags =
+        lib.optionals (lib.versionOlder version "9.0") [
+          "--enable-threads"
+        ]
+        ++ [
+          # Note: using $out instead of $man to prevent a runtime dependency on $man.
+          "--mandir=${placeholder "out"}/share/man"
+        ]
+        ++ lib.optionals (lib.versionOlder version "9.0") [
+          "--enable-man-symlinks"
+          # Don't install tzdata because NixOS already has a more up-to-date copy.
+          "--with-tzdata=no"
+        ]
+        ++ lib.optionals (lib.versionOlder version "8.6") [
+          # configure check broke due to GCC 14
+          "ac_cv_header_stdc=yes"
+        ]
+        ++ lib.optionals (lib.versionAtLeast version "9.0") [
+          # By default, tcl libraries get zipped and embedded into libtcl*.so,
+          # which gets `zipfs mount`ed at runtime. This is fragile (for example
+          # stripping the .so removes the zip trailer), so we install them as
+          # traditional files.
+          # This might make tcl slower to start from slower storage on cold cache,
+          # however according to my benchmarks on fast storage and warm cache
+          # tcl built with --disable-zipfs actually starts in half the time.
+          "--disable-zipfs"
+        ]
+        ++ [
+          # During cross compilation, the tcl build system assumes that libc
+          # functions are broken if it cannot test if they are broken or not and
+          # then causes a link error on static platforms due to symbol conflict.
+          # These functions are *checks notes* strtoul and strstr. These are
+          # never broken on modern platforms!
+          "tcl_cv_strtod_unbroken=ok"
+          "tcl_cv_strtoul_unbroken=ok"
+          "tcl_cv_strstr_unbroken=ok"
+        ]
+        ++ lib.optional stdenv.hostPlatform.is64bit "--enable-64bit";
 
-    enableParallelBuilding = true;
+      enableParallelBuilding = true;
 
-    postInstall =
-      let
-        dllExtension = stdenv.hostPlatform.extensions.sharedLibrary;
-        staticExtension = stdenv.hostPlatform.extensions.staticLibrary;
-      in
-      ''
-        make install-private-headers
-        ln -s $out/bin/tclsh${release} $out/bin/tclsh
-        if [[ -e $out/lib/libtcl${release}${staticExtension} ]]; then
-          ln -s $out/lib/libtcl${release}${staticExtension} $out/lib/libtcl${staticExtension}
-        fi
-        ${lib.optionalString (!stdenv.hostPlatform.isStatic) ''
-          ln -s $out/lib/libtcl${release}${dllExtension} $out/lib/libtcl${dllExtension}
-        ''}
-      '';
+      postInstall =
+        let
+          dllExtension = stdenv.hostPlatform.extensions.sharedLibrary;
+          dllDir = if stdenv.hostPlatform.isCygwin then "bin" else "lib";
+          staticExtension = stdenv.hostPlatform.extensions.staticLibrary;
+        in
+        ''
+          make install-private-headers
+          ln -s $out/bin/tclsh${release} $out/bin/tclsh
+          if [[ -e $out/lib/libtcl${release}${staticExtension} ]]; then
+            ln -s $out/lib/libtcl${release}${staticExtension} $out/lib/libtcl${staticExtension}
+          fi
+          ${
+            lib.optionalString (!stdenv.hostPlatform.isStatic) ''
+              ln -s $out/${dllDir}/libtcl${release}${dllExtension} $out/${dllDir}/libtcl${dllExtension}
+            ''
+            + lib.optionalString stdenv.hostPlatform.isCygwin ''
+              ln -s $out/${dllDir}/libtcl${release}${dllExtension} $out/lib/
+            ''
+          }
+        '';
 
-    meta = {
-      description = "Tcl scripting language";
-      homepage = "https://www.tcl.tk/";
-      license = lib.licenses.tcltk;
-      platforms = lib.platforms.all;
-      maintainers = with lib.maintainers; [ agbrooks ];
-    };
+      meta = {
+        description = "Tcl scripting language";
+        homepage = "https://www.tcl.tk/";
+        license = lib.licenses.tcltk;
+        platforms = lib.platforms.all;
+        maintainers = with lib.maintainers; [ agbrooks ];
+      };
 
-    passthru = rec {
-      inherit release version;
-      libPrefix = "tcl${release}";
-      libdir = "lib/${libPrefix}";
-      tclPackageHook = callPackage (
-        { buildPackages }:
-        makeSetupHook {
-          name = "tcl-package-hook";
-          propagatedBuildInputs = [ buildPackages.makeBinaryWrapper ];
-          meta = {
-            inherit (meta) maintainers platforms;
-          };
-        } ./tcl-package-hook.sh
-      ) { };
-      # verify that Tcl's clock library can access tzdata
-      tests.tzdata = runCommand "${pname}-test-tzdata" { } ''
-        ${baseInterp}/bin/tclsh <(echo "set t [clock scan {2004-10-30 05:00:00} \
-                                      -format {%Y-%m-%d %H:%M:%S} \
-                                      -timezone :America/New_York]") > $out
-      '';
-    };
-  };
+      passthru = rec {
+        inherit release version;
+        libPrefix = "tcl${release}";
+        libdir = "lib/${libPrefix}";
+        tclPackageHook = callPackage (
+          { buildPackages }:
+          makeSetupHook {
+            name = "tcl-package-hook";
+            propagatedBuildInputs = [ buildPackages.makeBinaryWrapper ];
+            meta = {
+              inherit (meta) maintainers platforms;
+            };
+          } ./tcl-package-hook.sh
+        ) { };
+        # verify that Tcl's clock library can access tzdata
+        tests.tzdata = runCommand "${pname}-test-tzdata" { } ''
+          ${baseInterp}/bin/tclsh <(echo "set t [clock scan {2004-10-30 05:00:00} \
+                                        -format {%Y-%m-%d %H:%M:%S} \
+                                        -timezone :America/New_York]") > $out
+        '';
+      };
+    }
+    // lib.optionalAttrs stdenv.hostPlatform.isCygwin {
+      patches = [
+        ./fix-cygwin-build.patch
+      ];
+    }
+  );
 
   mkTclDerivation = callPackage ./mk-tcl-derivation.nix { tcl = baseInterp; };
 
diff --git a/pkgs/development/libraries/icu/make-icu.nix b/pkgs/development/libraries/icu/make-icu.nix
index 00ba528081ac4..a6b8096857113 100644
--- a/pkgs/development/libraries/icu/make-icu.nix
+++ b/pkgs/development/libraries/icu/make-icu.nix
@@ -144,7 +144,13 @@ let
           substituteInPlace "$dev/bin/icu-config" \
             ${lib.concatMapStringsSep " " (r: "--replace '${r.from}' '${r.to}'") replacements}
         ''
-      );
+      )
+      # TODO: use MINGW_MOVEDLLSTOBINDIR?
+      + lib.optionalString stdenv.hostPlatform.isCygwin ''
+        mkdir -p "$out"/bin
+        set -x
+        mv "$out"/lib/cyg*.dll "$out"/bin/
+      '';
 
     postFixup = ''moveToOutput lib/icu "$dev" '';
   };
diff --git a/pkgs/development/libraries/libidn2/no-bootstrap-reference.nix b/pkgs/development/libraries/libidn2/no-bootstrap-reference.nix
index 7c01fddb75bd8..c322213522f2d 100644
--- a/pkgs/development/libraries/libidn2/no-bootstrap-reference.nix
+++ b/pkgs/development/libraries/libidn2/no-bootstrap-reference.nix
@@ -20,26 +20,32 @@ runCommandLocal "${libidn2.pname}-${libidn2.version}"
     };
     inherit (libidn2) meta;
   }
-  ''
-    cp -r '${libidn2.bin}' "$bin"
-    chmod +w "$bin"/bin/*
-    patchelf \
-      --set-interpreter '${stdenv.cc.bintools.dynamicLinker}' \
-      --set-rpath '${
-        lib.concatMapStringsSep ":" (p: lib.getLib p + "/lib") [
-          stdenv.cc.libc
-          libunistring
-          libidn2
-        ]
-      }' \
-      "$bin"/bin/*
+  (
+    ''
+      cp -r '${libidn2.bin}' "$bin"
+      chmod +w "$bin"/bin/*
+    ''
+    + lib.optionalString stdenv.hostPlatform.isElf ''
+      patchelf \
+        --set-interpreter '${stdenv.cc.bintools.dynamicLinker}' \
+        --set-rpath '${
+          lib.concatMapStringsSep ":" (p: lib.getLib p + "/lib") [
+            stdenv.cc.libc
+            libunistring
+            libidn2
+          ]
+        }' \
+        "$bin"/bin/*
+    ''
+    + ''
 
-    cp -r '${libidn2.dev}' "$dev"
-    chmod +w "$dev"/nix-support/propagated-build-inputs
-    substituteInPlace "$dev"/nix-support/propagated-build-inputs \
-      --replace '${libidn2.bin}' "$bin"
-    substituteInPlace "$dev"/lib/pkgconfig/libidn2.pc \
-      --replace '${libidn2.dev}' "$dev"
+      cp -r '${libidn2.dev}' "$dev"
+      chmod +w "$dev"/nix-support/propagated-build-inputs
+      substituteInPlace "$dev"/nix-support/propagated-build-inputs \
+        --replace '${libidn2.bin}' "$bin"
+      substituteInPlace "$dev"/lib/pkgconfig/libidn2.pc \
+        --replace '${libidn2.dev}' "$dev"
 
-    ln -s '${libidn2.out}' "$out" # it's hard to be without any $out
-  ''
+      ln -s '${libidn2.out}' "$out" # it's hard to be without any $out
+    ''
+  )
diff --git a/pkgs/development/libraries/libxcrypt/default.nix b/pkgs/development/libraries/libxcrypt/default.nix
index 4387d24a61e46..ec08231655e0a 100644
--- a/pkgs/development/libraries/libxcrypt/default.nix
+++ b/pkgs/development/libraries/libxcrypt/default.nix
@@ -64,7 +64,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   enableParallelBuilding = true;
 
-  doCheck = true;
+  doCheck = !stdenv.hostPlatform.isCygwin;
 
   passthru = {
     tests = {
diff --git a/pkgs/development/libraries/libxml2/common.nix b/pkgs/development/libraries/libxml2/common.nix
index bc43cfd9d6e3e..48a9cf7e1bd7c 100644
--- a/pkgs/development/libraries/libxml2/common.nix
+++ b/pkgs/development/libraries/libxml2/common.nix
@@ -49,7 +49,7 @@ stdenv'.mkDerivation (finalAttrs: {
   ++ lib.optional (enableStatic && enableShared) "static";
   outputMan = "bin";
 
-  patches = [ ] ++ extraPatches;
+  patches = [ ] ++ lib.optional stdenv.hostPlatform.isCygwin ./fix-cygwin-build.patch ++ extraPatches;
 
   strictDeps = true;
 
diff --git a/pkgs/development/libraries/libxml2/fix-cygwin-build.patch b/pkgs/development/libraries/libxml2/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..a1905964c0827
--- /dev/null
+++ b/pkgs/development/libraries/libxml2/fix-cygwin-build.patch
@@ -0,0 +1,12 @@
+diff --git a/globals.c b/globals.c
+index e0b05a2..546c8be 100644
+--- a/globals.c
++++ b/globals.c
+@@ -347,6 +347,7 @@ const xmlSAXLocator xmlDefaultSAXLocator = {
+  *
+  * Default old SAX v1 handler for HTML, builds the DOM tree
+  */
++XMLPUBVAR const xmlSAXHandlerV1 htmlDefaultSAXHandler;
+ const xmlSAXHandlerV1 htmlDefaultSAXHandler = {
+     xmlSAX2InternalSubset,
+     NULL,
diff --git a/pkgs/development/libraries/pcre2/default.nix b/pkgs/development/libraries/pcre2/default.nix
index 2c56ea3a7cc4f..3e00b4b353f8a 100644
--- a/pkgs/development/libraries/pcre2/default.nix
+++ b/pkgs/development/libraries/pcre2/default.nix
@@ -2,6 +2,7 @@
   lib,
   stdenv,
   fetchurl,
+  fetchpatch2,
   updateAutotoolsGnuConfigScriptsHook,
   # Causes consistent segfaults on ELFv1 PPC64 when trying to use Perl regex in gnugrep
   # https://github.com/PCRE2Project/pcre2/issues/762
@@ -17,6 +18,14 @@ stdenv.mkDerivation rec {
     hash = "sha256-FfvFq6a+7gsXrssEYCrjlDI5OroevY45t8q/fbiDKZ8=";
   };
 
+  ${if stdenv.hostPlatform.isCygwin then "patches" else null} =
+    lib.optional stdenv.hostPlatform.isCygwin
+      (fetchpatch2 {
+        url = "https://cygwin.com/cgit/cygwin-packages/pcre2/plain/pcre2-10.46-cygwin-jit.patch?id=45f4a0514d89311078f4a6d0bc4d12bcc2c3d4c6";
+        hash = "sha256-9fDAzjDgrM016IR8gCzEHn0ZrXhvwTdcjbzSlAV59Zg=";
+        stripLen = 1;
+      });
+
   nativeBuildInputs = [ updateAutotoolsGnuConfigScriptsHook ];
 
   configureFlags = [
diff --git a/pkgs/development/perl-modules/cygwin-checklib-fix.patch b/pkgs/development/perl-modules/cygwin-checklib-fix.patch
new file mode 100644
index 0000000000000..a14d2f33a519c
--- /dev/null
+++ b/pkgs/development/perl-modules/cygwin-checklib-fix.patch
@@ -0,0 +1,13 @@
+diff --git a/inc/Devel/CheckLib.pm b/inc/Devel/CheckLib.pm
+index 36a451a..a7554dc 100644
+--- a/inc/Devel/CheckLib.pm
++++ b/inc/Devel/CheckLib.pm
+@@ -379,7 +379,7 @@ sub _findcc {
+     my @cc = split( /\s+/, $Config{cc} );
+     return ( [ @cc, @ccflags ], \@ldflags ) if -x $cc[0];
+     foreach my $path (@paths) {
+-        my $compiler = File::Spec->catfile( $path, $cc[0] ) . $Config{_exe};
++        my $compiler = File::Spec->catfile( $path, $cc[0] );
+         return ( [ $compiler, @cc[ 1 .. $#cc ], @ccflags ], \@ldflags )
+           if -x $compiler;
+     }
diff --git a/pkgs/development/tcl-modules/by-name/ex/expect/fix-cygwin-build.patch b/pkgs/development/tcl-modules/by-name/ex/expect/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..018d22cef9895
--- /dev/null
+++ b/pkgs/development/tcl-modules/by-name/ex/expect/fix-cygwin-build.patch
@@ -0,0 +1,15 @@
+diff --git a/exp_win.c b/exp_win.c
+index 9ffad9f..b46d024 100644
+--- a/exp_win.c
++++ b/exp_win.c
+@@ -39,8 +39,8 @@ conflicts with sys/ioctl.h
+ /* Sigh.  On AIX 2.3, termios.h exists but does not define TIOCGWINSZ */
+ /* Instead, it has to come from ioctl.h.  However, As I said above, this */
+ /* can't be cavalierly included on all machines, even when it exists. */
+-/* Darwin also has termios.h, but it requires ioctl.h for `ioctl`. */
+-#if defined(HAVE_TERMIOS) && (defined(__APPLE__) || !defined(HAVE_TIOCGWINSZ_IN_TERMIOS_H))
++/* Darwin and Cygwin also have termios.h, but require ioctl.h for `ioctl`. */
++#if defined(HAVE_TERMIOS) && (defined(__APPLE__) || defined(__CYGWIN__) || !defined(HAVE_TIOCGWINSZ_IN_TERMIOS_H))
+ #  include <sys/ioctl.h>
+ #endif
+ 
diff --git a/pkgs/development/tcl-modules/by-name/ex/expect/package.nix b/pkgs/development/tcl-modules/by-name/ex/expect/package.nix
index a30305b890b75..6e614b0dc8411 100644
--- a/pkgs/development/tcl-modules/by-name/ex/expect/package.nix
+++ b/pkgs/development/tcl-modules/by-name/ex/expect/package.nix
@@ -38,7 +38,8 @@ tcl.mkTclDerivation rec {
     ./fix-darwin-bsd-clang16.patch
     # Remove some code which causes it to link against a file that does not exist at build time on native FreeBSD
     ./freebsd-unversioned.patch
-  ];
+  ]
+  ++ lib.optional stdenv.hostPlatform.isCygwin ./fix-cygwin-build.patch;
 
   postPatch = ''
     sed -i "s,/bin/stty,$(type -p stty),g" configure.in
diff --git a/pkgs/development/tools/misc/texinfo/common.nix b/pkgs/development/tools/misc/texinfo/common.nix
index 00dd5a5811a59..6c78eeee0521e 100644
--- a/pkgs/development/tools/misc/texinfo/common.nix
+++ b/pkgs/development/tools/misc/texinfo/common.nix
@@ -106,7 +106,9 @@ stdenv.mkDerivation {
     libiconv
     gawk
   ]
-  ++ optional interactive ncurses;
+  ++ optional interactive ncurses
+  # cygwin needs this so the perl DLL is in HOST_PATH for XS
+  ++ optional (!crossBuildTools && stdenv.hostPlatform.isCygwin) perl;
 
   configureFlags = [
     "PERL=${buildPackages.perl}/bin/perl"
diff --git a/pkgs/development/tools/parsing/flex/default.nix b/pkgs/development/tools/parsing/flex/default.nix
index fb1b9a601ac36..e6e50149c3859 100644
--- a/pkgs/development/tools/parsing/flex/default.nix
+++ b/pkgs/development/tools/parsing/flex/default.nix
@@ -7,6 +7,7 @@
   m4,
   autoreconfHook,
   help2man,
+  gettext,
 }:
 
 # Avoid 'fetchpatch' to allow 'flex' to be used as a possible 'gcc'
@@ -51,7 +52,11 @@ stdenv.mkDerivation rec {
     autoreconfHook
     help2man
   ];
-  buildInputs = [ bison ];
+  # TODO: instead of adding gettext, maybe just enable strictDeps?
+  # gettext on cygwin includes libintl, which is found through
+  # nativeBuildInputs, but if it's not in buildInputs it's unable to find
+  # cygintl-8.dll.
+  buildInputs = [ bison ] ++ lib.optional stdenv.hostPlatform.isCygwin gettext;
   propagatedBuildInputs = [ m4 ];
 
   preConfigure = lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) ''
@@ -59,7 +64,11 @@ stdenv.mkDerivation rec {
     export ac_cv_func_realloc_0_nonnull=yes
   '';
 
-  postConfigure = lib.optionalString (stdenv.hostPlatform.isDarwin || stdenv.hostPlatform.isCygwin) ''
+  ${if stdenv.hostPlatform.isCygwin then "configureFlags" else null} =
+    # from flex.cygport
+    lib.optional stdenv.hostPlatform.isCygwin "--disable-shared";
+
+  postConfigure = lib.optionalString (stdenv.hostPlatform.isDarwin) ''
     sed -i Makefile -e 's/-no-undefined//;'
   '';
 
diff --git a/pkgs/os-specific/cygwin/cygwin-dll-link.sh b/pkgs/os-specific/cygwin/cygwin-dll-link.sh
new file mode 100644
index 0000000000000..006dc0408cd0f
--- /dev/null
+++ b/pkgs/os-specific/cygwin/cygwin-dll-link.sh
@@ -0,0 +1,142 @@
+# shellcheck shell=bash
+
+_moveDLLsToLib() {
+  if [[ "${dontMoveDLLsToLib-}" ]]; then return; fi
+  # shellcheck disable=SC2154
+  moveToOutput "bin/*.dll" "${!outputLib}"
+}
+
+preFixupHooks+=(_moveDLLsToLib)
+
+declare _linkDeps_inputPath _linkDeps_outputPath
+
+_addOutputDLLPaths() {
+  for output in $(getAllOutputNames); do
+    addToSearchPath _linkDeps_outputPath "${!output}/bin"
+  done
+}
+
+preFixupHooks+=(_addOutputDLLPaths)
+
+_dllDeps() {
+  @objdump@ -p "$1" \
+    | sed -n 's/.*DLL Name: \(.*\)/\1/p' \
+    | sort -u
+}
+
+declare -Ag _linkDeps_visited
+
+_linkDeps() {
+  local target="$1" dir="$2"
+
+  # canonicalise these for the dictionary
+  target=$(realpath -s "$target")
+  dir=$(realpath -s "$dir")
+
+  if [[ -v _linkDeps_visited[$target] ]]; then
+    echo "_linkDeps: $target was already linked." 1>&2
+    return
+  fi
+  if [[ ! -f $target || ! -x $target ]]; then
+    echo "_linkDeps: $target is not an executable file, skipping." 1>&2
+    return
+  fi
+
+  local output inOutput
+  for output in $outputs ; do
+    if [[ $target == "${!output}"* && ! -L $target ]]; then
+      echo "_linkDeps: $target is in $output (${!output})." 1>&2
+      inOutput=1
+      break
+    fi
+  done
+
+  echo 'target:' "$target"
+  local dll
+  while read -r dll; do
+    echo '  dll:' "$dll"
+    local dllPath=$dir/$dll
+    if [[ -v _linkDeps_visited[$dllPath] ]]; then
+      echo "_linkDeps: $dll was already linked into $dir." 1>&2
+      continue
+    fi
+    if [[ -L $dllPath ]]; then
+      echo '    already linked'
+      dllPath=$(realpath -s "$(readlink "$dllPath")")
+      _linkDeps "$dllPath" "$dir"
+    elif [[ -e $dllPath ]]; then
+      echo '    already exits'
+      _linkDeps "$dllPath" "$dir"
+    else
+      if [[ $dll = cygwin1.dll ]]; then
+        dllPath=/bin/cygwin1.dll
+      else
+        # This intentionally doesn't use $dir because we want to prefer
+        # dependencies that are already linked next to the target.
+        local searchPath realTarget
+        searchPath=$_linkDeps_outputPath:$_linkDeps_inputPath:$HOST_PATH
+        if [[ -L $target ]]; then
+          searchPath=$searchPath:$(dirname "$(readlink "$target")")
+        fi
+        searchPath=$(dirname "$target"):$searchPath
+        if ! dllPath=$(PATH="$searchPath" type -P "$dll"); then
+          if [[ -z $inOutput || -n ${allowedImpureDLLsMap[$dll]} ]]; then
+            continue
+          fi
+          echo unable to find "$dll" in "$searchPath" >&2
+          exit 1
+        fi
+      fi
+      echo '    linking to:' "$dllPath"
+      CYGWIN+=\ winsymlinks:nativestrict ln -sr "$dllPath" "$dir"
+      _linkDeps "$dllPath" "$dir"
+    fi
+    _linkDeps_visited[$dir/$dll]=1
+  done < <(_dllDeps "$target")
+  wait $!
+}
+
+# linkDLLsDir can be used to override the destination path for links.  This is
+# useful if you're trying to link dependencies of libraries into the directory
+# containing an executable.
+#
+# Arguments can be a file or directory path. Directories are searched
+# recursively.
+linkDLLs() {
+  # shellcheck disable=SC2154
+  (
+    set -e
+    shopt -s globstar nullglob dotglob
+
+    local -a allowedImpureDLLsArray
+    concatTo allowedImpureDLLsArray allowedImpureDLLs
+
+    local -A allowedImpureDLLsMap;
+
+    for dll in "${allowedImpureDLLsArray[@]}"; do
+      allowedImpureDLLsMap[$dll]=1
+    done
+
+    local target file
+    for target in "$@"; do
+      # Iterate over any DLL that we depend on.
+      if [[ -f "$target" ]]; then
+        _linkDeps "$target" "${linkDLLsDir-$(dirname "$target")}"
+      elif [[ -d "$target" ]]; then
+        for file in "${target%/}"/**/*.{exe,dll}; do
+          _linkDeps "$file" "${linkDLLsDir-$(dirname "$file")}"
+        done
+      else
+        echo "linkDLLs: $target is not a file or directory, skipping." 1>&2
+      fi
+    done
+  )
+}
+
+_linkDLLs() {
+  # shellcheck disable=SC2154
+  if [[ ! -d $prefix || ${dontLinkDLLs-} ]]; then return; fi
+  linkDLLs "$prefix"/{bin,lib,libexec}/
+}
+
+fixupOutputHooks+=(_linkDLLs)
diff --git a/pkgs/os-specific/cygwin/default.nix b/pkgs/os-specific/cygwin/default.nix
index 09f69ff9f9b25..d8083ccd05de8 100644
--- a/pkgs/os-specific/cygwin/default.nix
+++ b/pkgs/os-specific/cygwin/default.nix
@@ -1,6 +1,10 @@
 {
+  lib,
   makeScopeWithSplicing',
   generateSplicesForMkScope,
+  makeSetupHook,
+  binutils-unwrapped,
+  stdenv,
 }:
 
 let
@@ -18,8 +22,17 @@ makeScopeWithSplicing' {
       w32api-headers = callPackage ./w32api { headersOnly = true; };
 
       newlib-cygwin = callPackage ./newlib-cygwin { };
-      # this is here to avoid symlinks being made to cygwin1.dll in /nix/store
-      newlib-cygwin-nobin = callPackage ./newlib-cygwin/nobin.nix { };
       newlib-cygwin-headers = callPackage ./newlib-cygwin { headersOnly = true; };
+
+      rebase = callPackage ./rebase { };
+
+      tests = callPackage ./tests { };
+
+      cygwinDllLinkHook = makeSetupHook {
+        name = "cygwin-dll-link-hook";
+        substitutions = {
+          objdump = "${lib.getBin binutils-unwrapped}/${stdenv.targetPlatform.config}/bin/objdump";
+        };
+      } ./cygwin-dll-link.sh;
     };
 }
diff --git a/pkgs/os-specific/cygwin/newlib-cygwin/Cygwin-only-use-native-symlinks-when-they-preserve-t.patch b/pkgs/os-specific/cygwin/newlib-cygwin/Cygwin-only-use-native-symlinks-when-they-preserve-t.patch
new file mode 100644
index 0000000000000..a19cdf05c18e9
--- /dev/null
+++ b/pkgs/os-specific/cygwin/newlib-cygwin/Cygwin-only-use-native-symlinks-when-they-preserve-t.patch
@@ -0,0 +1,52 @@
+From cc2ba5ca9926d696f3a4e1a431a67357e378eba7 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Mon, 6 Oct 2025 19:53:32 -0300
+Subject: [PATCH] Cygwin: only use native symlinks when they preserve the
+ target
+
+We want readlink() to return the original target string as much as
+possible. Currently it'll be changed in some common cases:
+
+x/ -> x
+x/../x -> x
+
+This doesn't normally break the links, but it means the link will change
+when archived. With Nix, this can change the hash of a NAR packed tree.
+---
+ winsup/cygwin/path.cc | 20 ++++++++++++++++++++
+ 1 file changed, 20 insertions(+)
+
+diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
+index 310876b5a..9af599572 100644
+--- a/winsup/cygwin/path.cc
++++ b/winsup/cygwin/path.cc
+@@ -1937,6 +1937,26 @@ symlink_native (const char *oldpath, path_conv &win32_newpath)
+   flags = win32_oldpath.isdir () ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0;
+   if (wincap.has_unprivileged_createsymlink ())
+     flags |= SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE;
++
++  {
++    char nfpath[SYMLINK_MAX + 1];
++    symlink_info sym;
++    int res = sys_wcstombs (nfpath, SYMLINK_MAX, final_oldpath->Buffer);
++    if (res > SYMLINK_MAX)
++      {
++	SetLastError (ERROR_FILE_NOT_FOUND);
++        final_newpath->Buffer[1] = L'?';
++        return -1;
++      }
++    res = sym.posixify (nfpath);
++    if (strcmp (sym.content (), oldpath))
++      {
++        SetLastError (ERROR_FILE_NOT_FOUND);
++        final_newpath->Buffer[1] = L'?';
++        return -1;
++      }
++  }
++
+   if (!CreateSymbolicLinkW (final_newpath->Buffer, final_oldpath->Buffer,
+ 			    flags))
+     {
+-- 
+2.50.1
+
diff --git a/pkgs/os-specific/cygwin/newlib-cygwin/default.nix b/pkgs/os-specific/cygwin/newlib-cygwin/default.nix
index 9869493c3be80..ad25645d978e5 100644
--- a/pkgs/os-specific/cygwin/newlib-cygwin/default.nix
+++ b/pkgs/os-specific/cygwin/newlib-cygwin/default.nix
@@ -1,30 +1,51 @@
 {
   lib,
-  stdenv,
   stdenvNoCC,
   stdenvNoLibc,
   autoreconfHook,
   bison,
   buildPackages,
-  cocom-tool-set,
   flex,
   perl,
   w32api,
   w32api-headers,
+  newlib-cygwin-headers,
 
   headersOnly ? false,
 }:
 
-(if headersOnly then stdenvNoCC else stdenvNoLibc).mkDerivation (
+let
+  stdenv =
+    let
+      bintools = stdenvNoLibc.cc.bintools.override {
+        libc = newlib-cygwin-headers;
+        noLibc = false;
+      };
+    in
+    # we only want to do this on cygwin because newlib-cygwin-headers doesn't
+    # evaluate on other platforms
+    stdenvNoLibc.override (
+      lib.optionalAttrs stdenvNoLibc.hostPlatform.isCygwin {
+        cc = stdenvNoLibc.cc.override {
+          libc = newlib-cygwin-headers;
+          noLibc = false;
+          inherit bintools;
+        };
+      }
+    );
+
+in
+(if headersOnly then stdenvNoCC else stdenv).mkDerivation (
   finalAttrs:
   {
     pname = "newlib-cygwin${lib.optionalString headersOnly "-headers"}";
     version = "3.6.4";
 
     src = buildPackages.fetchgit {
-      url = "https://cygwin.com/git/newlib-cygwin.git";
+      url = "git://cygwin.com/git/newlib-cygwin";
       rev = "cygwin-${finalAttrs.version}";
       hash = "sha256-+WYKwqcDAc7286GzbgKKAxNJCOf3AeNnF8XEVPoor+g=";
+      fetchSubmodules = false;
     };
 
     outputs = [
@@ -46,6 +67,9 @@
       # This is required for boost coroutines to work. After we get to the point
       # where nix runs on cygwin, we can attempt to upstream this again.
       ./store-tls-pointer-in-win32-tls.patch
+      ./Cygwin-only-use-native-symlinks-when-they-preserve-t.patch
+      # This fixes the nix libutil MonitorFdHup.shouldNotBlock test
+      ./fix-missing-POLLHUP-when-write-pipe-is-closed.patch
     ]
     # After cygwin hosted builds are working, we should upstream this
     ++ lib.optional (
@@ -114,11 +138,14 @@
         nativeBuildInputs = [
           autoreconfHook
           bison
-          cocom-tool-set
           flex
           perl
         ];
 
+        # -lintl from gettext breaks link on cygwin
+        ${if stdenv.buildPlatform.isCygwin then "dontAddExtraLibs" else null} =
+          stdenv.buildPlatform.isCygwin;
+
         buildInputs = [ w32api ];
 
         makeFlags = [
diff --git a/pkgs/os-specific/cygwin/newlib-cygwin/fix-missing-POLLHUP-when-write-pipe-is-closed.patch b/pkgs/os-specific/cygwin/newlib-cygwin/fix-missing-POLLHUP-when-write-pipe-is-closed.patch
new file mode 100644
index 0000000000000..c23b623c2a9b5
--- /dev/null
+++ b/pkgs/os-specific/cygwin/newlib-cygwin/fix-missing-POLLHUP-when-write-pipe-is-closed.patch
@@ -0,0 +1,90 @@
+diff --git a/winsup/cygwin/local_includes/fhandler.h b/winsup/cygwin/local_includes/fhandler.h
+index bdd87ebb7..3c505e545 100644
+--- a/winsup/cygwin/local_includes/fhandler.h
++++ b/winsup/cygwin/local_includes/fhandler.h
+@@ -456,6 +456,7 @@ public:
+   virtual class fhandler_timerfd *is_timerfd () { return NULL; }
+   virtual class fhandler_mqueue *is_mqueue () { return NULL; }
+   virtual int is_windows () {return 0; }
++  virtual bool is_hung_up () { return false; }
+ 
+   virtual void raw_read (void *ptr, size_t& ulen);
+   virtual ssize_t raw_write (const void *ptr, size_t ulen);
+@@ -723,6 +724,8 @@ class fhandler_socket_wsock: public fhandler_socket
+ 
+   fhandler_socket_wsock *is_wsock_socket () { return this; }
+ 
++  bool is_hung_up () { return saw_shutdown_read(); }
++
+   ssize_t recvfrom (void *ptr, size_t len, int flags,
+ 		    struct sockaddr *from, int *fromlen);
+   ssize_t recvmsg (struct msghdr *msg, int flags);
+@@ -1221,12 +1224,15 @@ class fhandler_pipe: public fhandler_pipe_fifo
+ {
+ private:
+   pid_t popen_pid;
++  bool hung_up = false;
+   void release_select_sem (const char *);
+ public:
+   fhandler_pipe ();
+ 
+   bool ispipe() const { return true; }
+   void set_pipe_buf_size ();
++  bool is_hung_up () { return hung_up; }
++  void set_hung_up () { hung_up = true; }
+ 
+   void set_popen_pid (pid_t pid) {popen_pid = pid;}
+   pid_t get_popen_pid () const {return popen_pid;}
+diff --git a/winsup/cygwin/poll.cc b/winsup/cygwin/poll.cc
+index a67507bbd..039958b1e 100644
+--- a/winsup/cygwin/poll.cc
++++ b/winsup/cygwin/poll.cc
+@@ -58,8 +58,7 @@ poll (struct pollfd *fds, nfds_t nfds, int timeout)
+ 	    FD_SET(fds[i].fd, read_fds);
+ 	  if (fds[i].events & POLLOUT)
+ 	    FD_SET(fds[i].fd, write_fds);
+-	  if (fds[i].events & POLLPRI)
+-	    FD_SET(fds[i].fd, except_fds);
++	  FD_SET(fds[i].fd, except_fds);
+ 	}
+       else if (fds[i].fd >= 0)
+ 	{
+@@ -99,9 +98,8 @@ poll (struct pollfd *fds, nfds_t nfds, int timeout)
+ 	  /* Check if the descriptor has been closed, or if shutdown for the
+ 	     read side has been called on a socket. */
+ 	  if (cygheap->fdtab.not_open (fds[i].fd)
+-	      || ((sock = cygheap->fdtab[fds[i].fd]->is_wsock_socket ())
+-		  && sock->saw_shutdown_read ()))
+-	    fds[i].revents = POLLHUP;
++				|| cygheap->fdtab[fds[i].fd]->is_hung_up())
++	    fds[i].revents |= POLLHUP;
+ 	  else
+ 	    {
+ 	      if ((fds[i].events & POLLIN) && FD_ISSET(fds[i].fd, read_fds))
+diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
+index 8a94ac076..6830669b8 100644
+--- a/winsup/cygwin/select.cc
++++ b/winsup/cygwin/select.cc
+@@ -749,6 +749,7 @@ peek_pipe (select_record *s, bool from_select)
+       if (n == PDA_ERROR)
+ 	{
+ 	  select_printf ("read: %s, n %d", fh->get_name (), n);
++	  ((fhandler_pipe *) fh)->set_hung_up ();
+ 	  if (s->except_selected)
+ 	    gotone += s->except_ready = true;
+ 	  if (s->read_selected)
+@@ -786,6 +787,14 @@ out:
+       if (n == PDA_ERROR && s->except_selected)
+ 	gotone += s->except_ready = true;
+     }
++
++  if (!s->read_selected && dev == FH_PIPER) {
++      ssize_t n = pipe_data_available (s->fd, fh, h, PDA_READ);
++      if (n == PDA_ERROR) {
++	((fhandler_pipe *) fh)->set_hung_up ();
++	gotone += s->except_ready = true;
++      }
++  }
+   return gotone;
+ }
+ 
diff --git a/pkgs/os-specific/cygwin/rebase/default.nix b/pkgs/os-specific/cygwin/rebase/default.nix
new file mode 100644
index 0000000000000..fd26fc8e3b897
--- /dev/null
+++ b/pkgs/os-specific/cygwin/rebase/default.nix
@@ -0,0 +1,22 @@
+{
+  autoreconfHook,
+  fetchgit,
+  lib,
+  stdenv,
+  w32api-headers,
+}:
+
+stdenv.mkDerivation rec {
+  pname = "rebase";
+  version = "4.6.6";
+
+  src = fetchgit {
+    url = "https://cygwin.com/git/cygwin-apps/rebase.git";
+    rev = "${pname}-${version}";
+    hash = "sha256-mZNPjgIwkUPOBZvMMVeVTXqJRu/sXVoZshm9Q1oa2u0=";
+  };
+
+  strictDeps = true;
+
+  nativeBuildInputs = [ autoreconfHook ];
+}
diff --git a/pkgs/os-specific/cygwin/tests/default.nix b/pkgs/os-specific/cygwin/tests/default.nix
new file mode 100644
index 0000000000000..a8744001dc2dc
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/default.nix
@@ -0,0 +1,130 @@
+{
+  dieHook,
+  lib,
+  stdenv,
+  testers,
+  runCommand,
+}:
+
+rec {
+  dll = stdenv.mkDerivation {
+    name = "dll";
+    src = ./dll;
+    outputs = [
+      "out"
+      "dev"
+    ];
+    buildInputs = [ dll2 ];
+    strictDeps = true;
+  };
+
+  dll2 = stdenv.mkDerivation {
+    name = "dll2";
+    src = ./dll2;
+    outputs = [
+      "out"
+      "dev"
+    ];
+  };
+
+  exe = stdenv.mkDerivation {
+    name = "exe";
+    src = ./exe;
+    buildInputs = [ dll ];
+    nativeBuildInputs = [ dieHook ];
+    strictDeps = true;
+    doCheck = true;
+    postFixup = ''[[ -e "$out"/bin/cyghello2.dll ]] || die missing indirect dependency'';
+  };
+
+  link-dll = exe.overrideAttrs {
+    name = "link-dll";
+    preFixup = ''
+      ln -s ${lib.getLib dll}/bin/cyghello.dll "$out"/bin/
+    '';
+  };
+
+  user32 = stdenv.mkDerivation {
+    name = "user32";
+    src = ./user32;
+    allowedImpureDLLs = [ "USER32.dll" ];
+  };
+
+  impure-dll = testers.testBuildFailure (
+    user32.overrideAttrs {
+      name = "impure-dll";
+      allowedImpureDLLs = [ ];
+    }
+  );
+
+  user32-dll = stdenv.mkDerivation {
+    name = "user32-dll";
+    src = ./user32-dll;
+    outputs = [
+      "out"
+      "dev"
+    ];
+    allowedImpureDLLs = [ "USER32.dll" ];
+  };
+
+  user32-exe = stdenv.mkDerivation {
+    name = "user32-exe";
+    src = ./user32-exe;
+    buildInputs = [ user32-dll ];
+    strictDeps = true;
+    doCheck = true;
+  };
+
+  link-dir-dll = exe.overrideAttrs {
+    name = "link-dir-dll";
+    preFixup = ''
+      mkdir "$out"/libexec
+      ln -s ${lib.getLib user32-dll}/bin/cygpeek.dll "$out"/libexec/
+      linkDLLsDir="$out"/bin linkDLLs "$out"/libexec/cygpeek.dll
+    '';
+  };
+
+  link-dir-exe = exe.overrideAttrs {
+    name = "link-dir-exe";
+    preFixup = ''
+      mkdir "$out"/libexec
+      ln -s ${lib.getLib user32-exe}/bin/{peek.exe,cygpeek.dll} "$out"/libexec/
+      linkDLLsDir="$out"/bin linkDLLs "$out"/libexec/peek.exe
+    '';
+  };
+
+  link-user32-dll = exe.overrideAttrs {
+    name = "link-user32-dll";
+    preFixup = ''
+      ln -s ${lib.getLib user32-dll}/bin/cygpeek.dll "$out"/bin/
+    '';
+  };
+
+  copy-dll-impure = testers.testBuildFailure (
+    user32-exe.overrideAttrs {
+      name = "copy-dll-impure";
+      preFixup = ''
+        cp ${lib.getLib user32-dll}/bin/cygpeek.dll "$out"/bin/
+      '';
+    }
+  );
+
+  copy-dll = user32-exe.overrideAttrs {
+    name = "copy-dll";
+    preFixup = ''
+      cp ${lib.getLib user32-dll}/bin/cygpeek.dll "$out"/bin/
+      linkDLLs "$out"/bin/cygpeek.dll
+    '';
+    allowedImpureDLLs = [ "USER32.dll" ];
+  };
+
+  double-link = user32-exe.overrideAttrs {
+    name = "double-link";
+    preFixup = ''linkDLLs "$out"'';
+  };
+
+  utf8-glob = runCommand "utf8-glob" { } ''
+    touch NetLock_Arany_=Class_Gold=_Főtanstvny:49412ce40010.crt
+    ls -l NetLock* > "$out"
+  '';
+}
diff --git a/pkgs/os-specific/cygwin/tests/dll/Makefile b/pkgs/os-specific/cygwin/tests/dll/Makefile
new file mode 100644
index 0000000000000..25e1e53c38e4b
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/dll/Makefile
@@ -0,0 +1,16 @@
+.PHONY: all install
+all: cyghello.dll
+
+install: $(out)/bin/cyghello.dll $(out)/lib/libhello.dll.a $(out)/include/hello.h
+
+cyghello.dll libhello.dll.a: hello.c
+	$(CC) -o $@ $^ -shared -Wl,--out-implib,libhello.dll.a -Wl,--export-all-symbols -lhello2
+
+$(out)/bin/cyghello.dll: cyghello.dll
+	install -m755 -D $< $@
+
+$(out)/lib/libhello.dll.a: libhello.dll.a
+	install -m644 -D $< $@
+
+$(out)/include/hello.h: hello.h
+	install -m644 -D $< $@
diff --git a/pkgs/os-specific/cygwin/tests/dll/hello.c b/pkgs/os-specific/cygwin/tests/dll/hello.c
new file mode 100644
index 0000000000000..db1a301c91a4d
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/dll/hello.c
@@ -0,0 +1,7 @@
+#include "hello.h"
+#include <stdio.h>
+#include <hello2.h>
+
+void hello() {
+				hello2();
+}
diff --git a/pkgs/os-specific/cygwin/tests/dll/hello.h b/pkgs/os-specific/cygwin/tests/dll/hello.h
new file mode 100644
index 0000000000000..a4a0b54c6052c
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/dll/hello.h
@@ -0,0 +1,2 @@
+#pragma once
+void hello();
diff --git a/pkgs/os-specific/cygwin/tests/dll2/Makefile b/pkgs/os-specific/cygwin/tests/dll2/Makefile
new file mode 100644
index 0000000000000..87c5c1a9b9ccf
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/dll2/Makefile
@@ -0,0 +1,16 @@
+.PHONY: all install
+all: cyghello2.dll
+
+install: $(out)/bin/cyghello2.dll $(out)/lib/libhello2.dll.a $(out)/include/hello2.h
+
+cyghello2.dll libhello2.dll.a: hello2.c
+	$(CC) -o $@ $^ -shared -Wl,--out-implib,libhello2.dll.a -Wl,--export-all-symbols
+
+$(out)/bin/cyghello2.dll: cyghello2.dll
+	install -m755 -D $< $@
+
+$(out)/lib/libhello2.dll.a: libhello2.dll.a
+	install -m644 -D $< $@
+
+$(out)/include/hello2.h: hello2.h
+	install -m644 -D $< $@
diff --git a/pkgs/os-specific/cygwin/tests/dll2/hello2.c b/pkgs/os-specific/cygwin/tests/dll2/hello2.c
new file mode 100644
index 0000000000000..d23050fbb7761
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/dll2/hello2.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+#include "hello2.h"
+
+void hello2() {
+				printf("Hello, World!\n");
+}
diff --git a/pkgs/os-specific/cygwin/tests/dll2/hello2.h b/pkgs/os-specific/cygwin/tests/dll2/hello2.h
new file mode 100644
index 0000000000000..34e200a07e95c
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/dll2/hello2.h
@@ -0,0 +1,2 @@
+#pragma once
+void hello2();
diff --git a/pkgs/os-specific/cygwin/tests/exe/Makefile b/pkgs/os-specific/cygwin/tests/exe/Makefile
new file mode 100644
index 0000000000000..da16b5d08c79b
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/exe/Makefile
@@ -0,0 +1,13 @@
+.PHONY: all check install
+all: hello.exe
+
+install: $(out)/bin/hello.exe
+
+hello.exe: main.c
+	$(CC) -o $@ $^ -lhello
+
+check: hello.exe
+	./hello.exe
+
+$(out)/bin/hello.exe: hello.exe
+	install -m755 -D $< $@
diff --git a/pkgs/os-specific/cygwin/tests/exe/main.c b/pkgs/os-specific/cygwin/tests/exe/main.c
new file mode 100644
index 0000000000000..9dbc882ea430e
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/exe/main.c
@@ -0,0 +1,6 @@
+#include <hello.h>
+
+int main() {
+				hello();
+				return 0;
+}
diff --git a/pkgs/os-specific/cygwin/tests/user32-dll/Makefile b/pkgs/os-specific/cygwin/tests/user32-dll/Makefile
new file mode 100644
index 0000000000000..483ad8854a060
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/user32-dll/Makefile
@@ -0,0 +1,16 @@
+.PHONY: all install
+all: cygpeek.dll
+
+install: $(out)/bin/cygpeek.dll $(out)/lib/libpeek.dll.a $(out)/include/peek.h
+
+cygpeek.dll libpeek.dll.a: peek.c
+	$(CC) -o $@ $^ -shared -Wl,--out-implib,libpeek.dll.a -Wl,--export-all-symbols
+
+$(out)/bin/cygpeek.dll: cygpeek.dll
+	install -m755 -D $< $@
+
+$(out)/lib/libpeek.dll.a: libpeek.dll.a
+	install -m644 -D $< $@
+
+$(out)/include/peek.h: peek.h
+	install -m644 -D $< $@
diff --git a/pkgs/os-specific/cygwin/tests/user32-dll/peek.c b/pkgs/os-specific/cygwin/tests/user32-dll/peek.c
new file mode 100644
index 0000000000000..715adb003c158
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/user32-dll/peek.c
@@ -0,0 +1,7 @@
+#include <windows.h>
+
+int peek()
+{
+				MSG msg;
+				PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE);
+}
diff --git a/pkgs/os-specific/cygwin/tests/user32-dll/peek.h b/pkgs/os-specific/cygwin/tests/user32-dll/peek.h
new file mode 100644
index 0000000000000..800f23f77da5d
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/user32-dll/peek.h
@@ -0,0 +1,2 @@
+#pragma once
+void peek();
diff --git a/pkgs/os-specific/cygwin/tests/user32-exe/Makefile b/pkgs/os-specific/cygwin/tests/user32-exe/Makefile
new file mode 100644
index 0000000000000..2316018189140
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/user32-exe/Makefile
@@ -0,0 +1,13 @@
+.PHONY: all check install
+all: peek.exe
+
+install: $(out)/bin/peek.exe
+
+peek.exe: main.c
+	$(CC) -o $@ $^ -lpeek
+
+check: peek.exe
+	./peek.exe
+
+$(out)/bin/peek.exe: peek.exe
+	install -m755 -D $< $@
diff --git a/pkgs/os-specific/cygwin/tests/user32-exe/main.c b/pkgs/os-specific/cygwin/tests/user32-exe/main.c
new file mode 100644
index 0000000000000..cddc78c91cabe
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/user32-exe/main.c
@@ -0,0 +1,6 @@
+#include <peek.h>
+
+int main() {
+				peek();
+				return 0;
+}
diff --git a/pkgs/os-specific/cygwin/tests/user32/Makefile b/pkgs/os-specific/cygwin/tests/user32/Makefile
new file mode 100644
index 0000000000000..6c696a2e8cd02
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/user32/Makefile
@@ -0,0 +1,13 @@
+.PHONY: all check install
+all: hello.exe
+
+install: $(out)/bin/hello.exe
+
+hello.exe: main.c
+	$(CC) -o $@ $^
+
+check: hello.exe
+	./hello.exe
+
+$(out)/bin/hello.exe: hello.exe
+	install -m755 -D $< $@
diff --git a/pkgs/os-specific/cygwin/tests/user32/main.c b/pkgs/os-specific/cygwin/tests/user32/main.c
new file mode 100644
index 0000000000000..9cc135770d21f
--- /dev/null
+++ b/pkgs/os-specific/cygwin/tests/user32/main.c
@@ -0,0 +1,7 @@
+#include <windows.h>
+
+int main()
+{
+				MSG msg;
+				PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE);
+}
diff --git a/pkgs/os-specific/cygwin/w32api/default.nix b/pkgs/os-specific/cygwin/w32api/default.nix
index bee2690076631..7318db70414b2 100644
--- a/pkgs/os-specific/cygwin/w32api/default.nix
+++ b/pkgs/os-specific/cygwin/w32api/default.nix
@@ -4,11 +4,33 @@
   stdenvNoLibc,
   autoreconfHook,
   windows,
+  newlib-cygwin-headers,
 
   headersOnly ? false,
 }:
 
-(if headersOnly then stdenvNoCC else stdenvNoLibc).mkDerivation (
+let
+  stdenv =
+    let
+      bintools = stdenvNoLibc.cc.bintools.override {
+        libc = newlib-cygwin-headers;
+        noLibc = false;
+      };
+    in
+    # we only want to do this on cygwin because newlib-cygwin-headers doesn't
+    # evaluate on other platforms
+    stdenvNoLibc.override (
+      lib.optionalAttrs stdenvNoLibc.hostPlatform.isCygwin {
+        cc = stdenvNoLibc.cc.override {
+          libc = newlib-cygwin-headers;
+          noLibc = false;
+          inherit bintools;
+        };
+      }
+    );
+
+in
+(if headersOnly then stdenvNoCC else stdenv).mkDerivation (
   {
     pname = "w32api${lib.optionalString headersOnly "-headers"}";
 
@@ -27,8 +49,8 @@
     enableParallelBuilding = true;
 
     passthru = {
-      incdir = "/include/w32api/";
-      libdir = "/lib/w32api/";
+      incdir = "/include/w32api";
+      libdir = "/lib/w32api";
     };
 
     meta = {
@@ -51,7 +73,7 @@
       }
     else
       {
-        nativeBuildInputs = [ autoreconfHook ];
+        # nativeBuildInputs = [ autoreconfHook ];
 
         hardeningDisable = [
           "stackprotector"
diff --git a/pkgs/stdenv/cross/default.nix b/pkgs/stdenv/cross/default.nix
index cc53957eee0dc..b194c780a3196 100644
--- a/pkgs/stdenv/cross/default.nix
+++ b/pkgs/stdenv/cross/default.nix
@@ -83,7 +83,10 @@ lib.init bootStages
                   || p.isGenode;
               in
               f hostPlatform && !(f buildPlatform)
-            ) buildPackages.updateAutotoolsGnuConfigScriptsHook;
+            ) buildPackages.updateAutotoolsGnuConfigScriptsHook
+            ++ lib.optional (
+              hostPlatform.isCygwin && !buildPlatform.isCygwin
+            ) buildPackages.cygwin.cygwinDllLinkHook;
         })
       );
     in
diff --git a/pkgs/stdenv/cygwin/default.nix b/pkgs/stdenv/cygwin/default.nix
new file mode 100644
index 0000000000000..d3e1943d1c0c8
--- /dev/null
+++ b/pkgs/stdenv/cygwin/default.nix
@@ -0,0 +1,530 @@
+{
+  lib,
+  localSystem,
+  crossSystem,
+  config,
+  overlays,
+  crossOverlays ? [ ],
+  bootstrapFiles ?
+    let
+      table = {
+        x86_64-cygwin = {
+          # import ./bootstrap-files/x86_64-pc-cygwin.nix;
+          unpack = import <nix/fetchurl.nix> {
+            url = "https://github.com/corngood/nixpkgs/releases/download/bootstrap%2Fv0.1/unpack.nar.xz";
+            hash = "sha256-B5pezEcJkWtI0nDRCeOjtwSQ4OTuA2ef06keEvr4i4E=";
+            name = "unpack";
+            unpack = true;
+          };
+        };
+      };
+      files =
+        table.${localSystem.system}
+          or (throw "unsupported platform ${localSystem.system} for the cygwin stdenv");
+    in
+    files,
+}:
+
+assert crossSystem == localSystem;
+let
+  cygwinDllLink = derivation {
+    inherit (localSystem) system;
+    name = "cygwin-dll-link.sh";
+    src = ../../os-specific/cygwin/cygwin-dll-link.sh;
+    builder = "${bootstrapFiles.unpack}/bin/bash";
+    args = [
+      "-c"
+      "sed s:@objdump@:${bootstrapFiles.unpack}/bin/objdump:g $src > $out"
+    ];
+    PATH = "${bootstrapFiles.unpack}/bin";
+  };
+  linkBootstrap = (
+    attrs:
+    derivation (
+      attrs
+      // {
+        inherit (localSystem) system;
+        name = attrs.name or (baseNameOf (builtins.elemAt attrs.paths 0));
+        version = "bootstrap";
+        src = bootstrapFiles.unpack;
+        builder = "${bootstrapFiles.unpack}/bin/bash";
+        args = [
+          ./linkBootstrap.sh
+        ];
+        PATH = "${bootstrapFiles.unpack}/bin";
+        inherit cygwinDllLink;
+        paths = attrs.paths;
+      }
+    )
+  );
+
+  bootstrap-packages = {
+    bashNonInteractive = linkBootstrap {
+      paths = [
+        "bin/bash"
+        "bin/sh"
+      ];
+      shell = "bin/bash";
+      shellPath = "/bin/bash";
+    };
+    binutils-unwrapped = linkBootstrap {
+      name = "binutils";
+      paths = map (str: "bin/" + str) [
+        "ld"
+        "as"
+        "addr2line"
+        "ar"
+        "c++filt"
+        "dlltool"
+        "elfedit"
+        "gprof"
+        "objdump"
+        "nm"
+        "objcopy"
+        "ranlib"
+        "readelf"
+        "size"
+        "strings"
+        "strip"
+        "windres"
+      ];
+    };
+    bzip2.bin = linkBootstrap { paths = [ "bin/bzip2" ]; };
+    coreutils = linkBootstrap {
+      name = "coreutils";
+      paths = map (str: "bin/" + str) [
+        "base64"
+        "basename"
+        "cat"
+        "chcon"
+        "chgrp"
+        "chmod"
+        "chown"
+        "chroot"
+        "cksum"
+        "comm"
+        "cp"
+        "csplit"
+        "cut"
+        "date"
+        "dd"
+        "df"
+        "dir"
+        "dircolors"
+        "dirname"
+        "du"
+        "echo"
+        "env"
+        "expand"
+        "expr"
+        "factor"
+        "false"
+        "fmt"
+        "fold"
+        "groups"
+        "head"
+        "hostid"
+        "id"
+        "install"
+        "join"
+        "kill"
+        "link"
+        "ln"
+        "logname"
+        "ls"
+        "md5sum"
+        "mkdir"
+        "mkfifo"
+        "mknod"
+        "mktemp"
+        "mv"
+        "nice"
+        "nl"
+        "nohup"
+        "nproc"
+        "numfmt"
+        "od"
+        "paste"
+        "pathchk"
+        "pinky"
+        "pr"
+        "printenv"
+        "printf"
+        "ptx"
+        "pwd"
+        "readlink"
+        "realpath"
+        "rm"
+        "rmdir"
+        "runcon"
+        "seq"
+        "shred"
+        "shuf"
+        "sleep"
+        "sort"
+        "split"
+        "stat"
+        "stty"
+        "sum"
+        "tac"
+        "tail"
+        "tee"
+        "test"
+        "timeout"
+        "touch"
+        "tr"
+        "true"
+        "truncate"
+        "tsort"
+        "tty"
+        "uname"
+        "unexpand"
+        "uniq"
+        "unlink"
+        "users"
+        "vdir"
+        "wc"
+        "who"
+        "whoami"
+        "yes"
+        "["
+      ];
+    };
+    curl = linkBootstrap {
+      paths = [
+        "bin/curl"
+      ];
+    };
+    diffutils = linkBootstrap {
+      name = "diffutils";
+      paths = map (str: "bin/" + str) [
+        "diff"
+        "cmp"
+        #"diff3"
+        #"sdiff"
+      ];
+    };
+    # expand-response-params = bootstrapFiles.unpack;
+    file = linkBootstrap {
+      name = "file";
+      paths = [ "bin/file" ];
+    };
+    findutils = linkBootstrap {
+      name = "findutils";
+      paths = [
+        "bin/find"
+        "bin/xargs"
+      ];
+    };
+    gawk = linkBootstrap {
+      paths = [
+        "bin/awk"
+        "bin/gawk"
+      ];
+    };
+    gcc-unwrapped = linkBootstrap {
+      name = "gcc";
+      paths = map (str: "bin/" + str) [
+        "gcc"
+        "g++"
+        "cygatomic-1.dll"
+        "cyggcc_s-seh-1.dll"
+        "cygquadmath-0.dll"
+        "cygstdc++-6.dll"
+      ];
+    };
+    git = linkBootstrap { paths = [ "bin/git" ]; };
+    gnugrep = linkBootstrap {
+      paths = [
+        "bin/grep"
+        "bin/egrep"
+        "bin/fgrep"
+      ];
+    };
+    gnumake = linkBootstrap { paths = [ "bin/make" ]; };
+    gnused = linkBootstrap { paths = [ "bin/sed" ]; };
+    gnutar = linkBootstrap { paths = [ "bin/tar" ]; };
+    gzip = linkBootstrap {
+      paths = [
+        "bin/gzip"
+        #"bin/gunzip"
+      ];
+      postBuild = ''
+        rm "$out"/bin/gzip
+        sed -E 's:/nix/store/[^/]*:'$src':' "$src"/bin/gzip > "$out"/bin/gzip
+        chmod +x "$out"/bin/gzip
+      '';
+    };
+    libc = linkBootstrap {
+      name = "libc";
+      paths = [
+        "include"
+        "lib"
+      ];
+    };
+    patch = linkBootstrap { paths = [ "bin/patch" ]; };
+    xz.bin = linkBootstrap { paths = [ "bin/xz" ]; };
+  };
+
+in
+[
+  (
+    prevStage:
+    let
+      initialPath =
+        # TODO: switch to this
+        # ((import ../generic/common-path.nix) { pkgs = bootstrap-packages; })
+        with bootstrap-packages;
+        [
+          coreutils
+          diffutils
+          gnutar
+          file
+          findutils
+          gnumake
+          gnused
+          gnugrep
+          gawk
+          patch
+          bashNonInteractive
+          gzip
+          bzip2.bin
+          xz.bin
+        ]
+        # needed for cygwin1.dll
+        # TODO: remove?
+        ++ [ "/" ];
+
+      shell = "${bootstrap-packages.bashNonInteractive}/bin/bash";
+
+      stdenvNoCC = import ../generic rec {
+        name = "stdenv-cygwin-boot0";
+
+        buildPlatform = localSystem;
+        hostPlatform = localSystem;
+        targetPlatform = localSystem;
+        inherit
+          config
+          initialPath
+          fetchurlBoot
+          shell
+          ;
+
+        hasCC = false;
+        cc = null;
+
+        extraNativeBuildInputs = [
+          cygwinDllLink
+        ];
+
+        overrides = self: super: {
+          fetchurl = lib.makeOverridable fetchurlBoot;
+          fetchgit = super.fetchgit.override {
+            inherit (bootstrap-packages) git;
+            cacert = null;
+            git-lfs = null;
+          };
+        };
+      };
+
+      fetchurlBoot = import ../../build-support/fetchurl {
+        inherit lib stdenvNoCC;
+        inherit (bootstrap-packages) curl;
+        inherit (config) rewriteURL hashedMirrors;
+      };
+
+    in
+    {
+      inherit config overlays stdenvNoCC;
+      stdenv = stdenvNoCC;
+    }
+  )
+
+  (prevStage: {
+    inherit config overlays;
+    inherit (prevStage) stdenvNoCC;
+
+    stdenv = import ../generic rec {
+      name = "stdenv-cygwin-boot1";
+
+      inherit config;
+      inherit (prevStage.stdenv)
+        buildPlatform
+        hostPlatform
+        targetPlatform
+        fetchurlBoot
+        initialPath
+        shell
+        ;
+
+      extraNativeBuildInputs = [
+        cygwinDllLink
+      ];
+
+      cc = lib.makeOverridable (import ../../build-support/cc-wrapper) {
+        inherit lib;
+        inherit (prevStage) stdenvNoCC;
+        name = "${name}-cc";
+        cc = bootstrap-packages.gcc-unwrapped;
+        isGNU = true;
+        libc = prevStage.cygwin.newlib-cygwin-headers;
+        inherit (bootstrap-packages) gnugrep coreutils;
+        expand-response-params = "";
+        nativeTools = false;
+        nativeLibc = false;
+        propagateDoc = false;
+        runtimeShell = shell;
+        bintools = lib.makeOverridable (import ../../build-support/bintools-wrapper) {
+          inherit lib;
+          inherit (prevStage) stdenvNoCC;
+          name = "${name}-bintools";
+          bintools = bootstrap-packages.binutils-unwrapped;
+          libc = prevStage.cygwin.newlib-cygwin-headers;
+          inherit (bootstrap-packages) gnugrep coreutils;
+          expand-response-params = "";
+          nativeTools = false;
+          nativeLibc = false;
+          propagateDoc = false;
+          runtimeShell = shell;
+        };
+      };
+
+      overrides = self: super: {
+        fetchurl = lib.makeOverridable fetchurlBoot;
+        fetchgit = super.fetchgit.override {
+          inherit (bootstrap-packages) git;
+          cacert = null;
+          git-lfs = null;
+        };
+      };
+    };
+  })
+
+  (prevStage: {
+    inherit config overlays;
+
+    stdenv = import ../generic rec {
+      name = "stdenv-cygwin-boot2";
+
+      buildPlatform = localSystem;
+      hostPlatform = localSystem;
+      targetPlatform = localSystem;
+      inherit config;
+      inherit (prevStage.stdenv) fetchurlBoot initialPath shell;
+
+      extraNativeBuildInputs = [
+        cygwinDllLink
+      ];
+
+      cc = lib.makeOverridable (import ../../build-support/cc-wrapper) {
+        inherit lib;
+        inherit (prevStage) stdenvNoCC;
+        name = "${name}-cc";
+        cc = bootstrap-packages.gcc-unwrapped;
+        isGNU = true;
+        libc = bootstrap-packages.libc // {
+          inherit (prevStage.cygwin) w32api;
+        };
+        inherit (bootstrap-packages) gnugrep coreutils;
+        expand-response-params = "";
+        nativeTools = false;
+        nativeLibc = false;
+        propagateDoc = false;
+        runtimeShell = shell;
+        bintools = lib.makeOverridable (import ../../build-support/bintools-wrapper) {
+          inherit lib;
+          inherit (prevStage) stdenvNoCC;
+          name = "${name}-bintools";
+          bintools = bootstrap-packages.binutils-unwrapped;
+          libc = bootstrap-packages.libc // {
+            inherit (prevStage.cygwin) w32api;
+          };
+          inherit (bootstrap-packages) gnugrep coreutils;
+          expand-response-params = "";
+          nativeTools = false;
+          nativeLibc = false;
+          propagateDoc = false;
+          runtimeShell = shell;
+        };
+      };
+
+      overrides = self: super: {
+        fetchurl = lib.makeOverridable fetchurlBoot;
+        __realFetchUrl = super.fetchurl;
+        fetchgit = super.fetchgit.override {
+          inherit (bootstrap-packages) git;
+          cacert = null;
+          git-lfs = null;
+        };
+      };
+    };
+  })
+
+  (prevStage: {
+    inherit config overlays;
+
+    stdenv = import ../generic rec {
+      name = "stdenv-cygwin-boot3";
+
+      buildPlatform = localSystem;
+      hostPlatform = localSystem;
+      targetPlatform = localSystem;
+      inherit config;
+
+      initialPath = ((import ../generic/common-path.nix) { pkgs = prevStage; });
+
+      extraNativeBuildInputs = [
+        prevStage.cygwin.cygwinDllLinkHook
+      ];
+
+      cc = prevStage.gcc;
+
+      shell = cc.shell;
+
+      inherit (prevStage.stdenv) fetchurlBoot;
+
+      overrides = self: super: {
+        inherit (prevStage) fetchurl;
+        __realFetchUrl = super.fetchurl;
+      };
+    };
+  })
+
+  (prevStage: {
+    inherit config overlays;
+
+    stdenv = import ../generic rec {
+      name = "stdenv-cygwin";
+
+      buildPlatform = localSystem;
+      hostPlatform = localSystem;
+      targetPlatform = localSystem;
+      inherit config;
+
+      initialPath = ((import ../generic/common-path.nix) { pkgs = prevStage; });
+
+      extraNativeBuildInputs = [
+        prevStage.cygwin.cygwinDllLinkHook
+      ];
+
+      cc = prevStage.gcc.override (old: {
+        cc = old.cc.overrideAttrs (old: {
+          # break dependency on previous stage cygintl-8.dll
+          preFixup = old.preFixup or "" + ''
+            ln -s "${lib.getLib prevStage.gettext}"/bin/cygintl-8.dll "$out"/bin
+          '';
+        });
+      });
+
+      shell = cc.shell;
+
+      inherit (prevStage.stdenv) fetchurlBoot;
+
+      disallowedRequisites = [ bootstrapFiles.unpack ];
+
+      overrides = self: super: {
+        fetchurl = prevStage.__realFetchUrl;
+      };
+    };
+  })
+]
diff --git a/pkgs/stdenv/cygwin/linkBootstrap.sh b/pkgs/stdenv/cygwin/linkBootstrap.sh
new file mode 100755
index 0000000000000..de112c83d8f52
--- /dev/null
+++ b/pkgs/stdenv/cygwin/linkBootstrap.sh
@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+
+for path in $paths; do
+  if [[ -e $src/$path.exe ]]; then
+    path=$path.exe
+  fi
+  if ! [[ -e $src/$path ]]; then
+    echo "Error: $path does not exist"
+    exit 1
+  fi
+  mkdir -p $out/$(dirname $path)
+  CYGWIN+=\ winsymlinks:nativestrict ln -s $src/$path $out/$path
+done
+
+addEnvHooks() {
+  true
+}
+
+# HACK: copied from stdenv
+# refactor cygwin-dll-link?
+concatTo() {
+    local -
+    set -o noglob
+    local -n targetref="$1"; shift
+    local arg default name type
+    for arg in "$@"; do
+        IFS="=" read -r name default <<< "$arg"
+        local -n nameref="$name"
+        if [[ -z "${nameref[*]}" && -n "$default" ]]; then
+            targetref+=( "$default" )
+        elif type=$(declare -p "$name" 2> /dev/null); then
+            case "${type#* }" in
+                -A*)
+                    echo "concatTo(): ERROR: trying to use concatTo on an associative array." >&2
+                    return 1 ;;
+                -a*)
+                    targetref+=( "${nameref[@]}" ) ;;
+                *)
+                    if [[ "$name" = *"Array" ]]; then
+                        nixErrorLog "concatTo(): $name is not declared as array, treating as a singleton. This will become an error in future"
+                        # Reproduces https://github.com/NixOS/nixpkgs/pull/318614/files#diff-7c7ca80928136cfc73a02d5b28350bd900e331d6d304857053ffc9f7beaad576L359
+                        targetref+=( ${nameref+"${nameref[@]}"} )
+                    else
+                        # shellcheck disable=SC2206
+                        targetref+=( ${nameref-} )
+                    fi
+                    ;;
+            esac
+        fi
+    done
+}
+
+source "$cygwinDllLink"
+
+_linkDeps_inputPath=$src/bin
+allowedImpureDLLs=(KERNEL32.dll ntdll.dll)
+linkDLLs $out/bin
+
+[[ ! -v postBuild ]] || eval "$postBuild"
diff --git a/pkgs/stdenv/cygwin/make-bootstrap-tools-cross.nix b/pkgs/stdenv/cygwin/make-bootstrap-tools-cross.nix
new file mode 100644
index 0000000000000..c133be97d600c
--- /dev/null
+++ b/pkgs/stdenv/cygwin/make-bootstrap-tools-cross.nix
@@ -0,0 +1,30 @@
+{
+  system ? builtins.currentSystem,
+}:
+
+let
+  inherit (releaseLib) lib;
+  releaseLib = import ../../top-level/release-lib.nix {
+    # We're not using any functions from release-lib.nix that look at
+    # supportedSystems.
+    supportedSystems = [ ];
+  };
+
+  make =
+    crossSystem:
+    import ./make-bootstrap-tools.nix {
+      pkgs = releaseLib.pkgsForCross crossSystem system;
+    };
+in
+lib.mapAttrs (n: make) (
+  with lib.systems.examples;
+  {
+    # NOTE: Only add platforms for which there are files in `./bootstrap-files`
+    # or for which you plan to request the tarball upload soon. See the
+    #   maintainers/scripts/bootstrap-files/README.md
+    # on how to request an upload.
+    # Sort following the sorting in `./default.nix` `bootstrapFiles` argument.
+
+    x86_64-pc-cygwin = x86_64-cygwin;
+  }
+)
diff --git a/pkgs/stdenv/cygwin/make-bootstrap-tools.nix b/pkgs/stdenv/cygwin/make-bootstrap-tools.nix
new file mode 100644
index 0000000000000..daf2df80f4fe8
--- /dev/null
+++ b/pkgs/stdenv/cygwin/make-bootstrap-tools.nix
@@ -0,0 +1,99 @@
+{
+  pkgs ? import ../../.. { },
+}:
+let
+  inherit (pkgs) runCommand;
+  # splicing doesn't seem to work right here
+  inherit (pkgs.buildPackages) dumpnar rsync nukeReferences;
+
+  unpacked =
+    let
+      inherit (pkgs)
+        bashNonInteractive
+        binutils-unwrapped
+        bzip2
+        coreutils
+        diffutils
+        file
+        findutils
+        gawk
+        gcc-unwrapped
+        gitMinimal # for fetchgit (newlib-cygwin)
+        gnugrep
+        gnumake
+        gnused
+        gnutar
+        gzip
+        patch
+        xz
+        ;
+
+      inherit (pkgs.cygwin)
+        newlib-cygwin
+        w32api
+        ;
+
+      curl = pkgs.curl.overrideAttrs (old: {
+        # these use the build shebang
+        # TODO: fix in curl
+        postFixup = old.postFixup or "" + ''
+          rm "$dev"/bin/curl-config "$bin"/bin/wcurl
+        '';
+      });
+
+    in
+    runCommand "unpacked"
+      {
+        nativeBuildInputs = [ nukeReferences ];
+        # The result should not contain any references (store paths) so
+        # that we can safely copy them out of the store and to other
+        # locations in the store.
+        allowedReferences = [ ];
+        strictDeps = true;
+      }
+      ''
+        mkdir -p "$out"/{bin,include,lib,libexec}
+        cp -d "${bashNonInteractive}"/bin/* "$out"/bin/
+        cp -d "${binutils-unwrapped}"/bin/* "$out"/bin/
+        cp -d "${bzip2}"/bin/* "$out"/bin/
+        cp -d "${coreutils}"/bin/* "$out"/bin/
+        cp -d "${curl}"/bin/* "$out"/bin/
+        cp -d "${diffutils}"/bin/* "$out"/bin/
+        cp -d "${file}"/bin/* "$out"/bin/
+        cp -d "${findutils}"/bin/* "$out"/bin/
+        cp -d "${gawk}"/bin/* "$out"/bin/
+        cp -d "${gcc-unwrapped}"/bin/* "$out"/bin/
+        cp -rd ${gcc-unwrapped}/include/* $out/include/
+        cp -rd ${gcc-unwrapped}/lib/* $out/lib/
+        cp -rd ${gcc-unwrapped}/libexec/* $out/libexec/
+        cp -frd ${gcc-unwrapped.lib}/bin/* $out/bin/
+        cp -rd ${gcc-unwrapped.lib}/lib/* $out/lib/
+        cp -d "${gitMinimal}"/bin/* "$out"/bin/
+        cp -d "${gnugrep}"/bin/* "$out"/bin/
+        cp -d "${gnumake}"/bin/* "$out"/bin/
+        cp -d "${gnused}"/bin/* "$out"/bin/
+        cp -d "${gnutar}"/bin/* "$out"/bin/
+        (shopt -s dotglob; cp -d "${gzip}"/bin/* "$out"/bin/)
+        cp -rd ${newlib-cygwin.dev}/include/* $out/include/
+        cp -rd ${newlib-cygwin}/lib/* "$out"/lib/
+        cp -d "${patch}"/bin/* "$out"/bin/
+        cp -d "${w32api}"/lib/w32api/lib{advapi,shell,user,kernel}32.a "$out"/lib/
+        cp -d "${xz}"/bin/* "$out"/bin/
+
+        chmod -R +w "$out"
+
+        find "$out" -type l -print0 | while read -d $'\0' link; do
+          [[ -L "$link" && -e "$link" ]] || continue
+          [[ $(realpath "$link") != "$out"* ]] || continue
+          cp "$link" "$link"~
+          mv "$link"~ "$link"
+        done
+
+        find "$out" -print0 | xargs -0 nuke-refs -e "$out"
+      '';
+in
+{
+  unpack = runCommand "unpack.nar.xz" {
+    nativeBuildInputs = [ dumpnar ];
+  } "dumpnar ${unpacked} | xz -9 -e -T $NIX_BUILD_CORES >$out";
+}
diff --git a/pkgs/stdenv/default.nix b/pkgs/stdenv/default.nix
index 3cbe274a2f0e8..80004c25ebdfb 100644
--- a/pkgs/stdenv/default.nix
+++ b/pkgs/stdenv/default.nix
@@ -50,13 +50,13 @@ else if localSystem.isLinux then
   stagesLinux
 else if localSystem.isDarwin then
   stagesDarwin
+else if localSystem.isCygwin then
+  (import ./cygwin args)
 # misc special cases
 else
   {
     # switch
     x86_64-solaris = stagesNix;
-    i686-cygwin = stagesNative;
-    x86_64-cygwin = stagesNative;
     x86_64-freebsd = stagesFreeBSD;
   }
   .${localSystem.system} or stagesNative
diff --git a/pkgs/stdenv/generic/default.nix b/pkgs/stdenv/generic/default.nix
index d28af17692cbe..6adc1127e7aee 100644
--- a/pkgs/stdenv/generic/default.nix
+++ b/pkgs/stdenv/generic/default.nix
@@ -84,7 +84,7 @@ let
           ../../build-support/setup-hooks/set-source-date-epoch-to-latest.sh
           ../../build-support/setup-hooks/strip.sh
         ]
-        ++ lib.optionals hasCC [ cc ];
+        ++ lib.optionals (hasCC && cc != null) [ cc ];
 
       defaultBuildInputs = extraBuildInputs;
 
diff --git a/pkgs/stdenv/generic/make-derivation.nix b/pkgs/stdenv/generic/make-derivation.nix
index cdfeb34a24116..6b4f9acdc4b05 100644
--- a/pkgs/stdenv/generic/make-derivation.nix
+++ b/pkgs/stdenv/generic/make-derivation.nix
@@ -475,7 +475,7 @@ let
           nativeBuildInputs
           ++ optional separateDebugInfo' ../../build-support/setup-hooks/separate-debug-info.sh
           ++ optional isWindows ../../build-support/setup-hooks/win-dll-link.sh
-          ++ optional isCygwin ../../build-support/setup-hooks/cygwin-dll-link.sh
+          ++ optional (isCygwin && canExecuteHostOnBuild) ../../build-support/setup-hooks/cygwin-dll-path.sh
           ++ optionals doCheck nativeCheckInputs
           ++ optionals doInstallCheck nativeInstallCheckInputs;
 
@@ -705,7 +705,6 @@ let
               allowedImpureDLLs
               ++ lib.optionals isCygwin [
                 "KERNEL32.dll"
-                "cygwin1.dll"
               ];
           }
           // (
diff --git a/pkgs/tools/compression/xz/default.nix b/pkgs/tools/compression/xz/default.nix
index ed8fc7a0bab60..6e23ddc862db3 100644
--- a/pkgs/tools/compression/xz/default.nix
+++ b/pkgs/tools/compression/xz/default.nix
@@ -33,7 +33,11 @@ stdenv.mkDerivation (finalAttrs: {
     "doc"
   ];
 
-  configureFlags = lib.optional enableStatic "--disable-shared";
+  configureFlags =
+    lib.optional enableStatic "--disable-shared"
+    # If cygpath isn't available, libtool tries to run cmd.exe for this test,
+    # but neither are in stdenv.
+    ++ lib.optional stdenv.buildPlatform.isCygwin "lt_cv_cmd_slashes=one";
 
   enableParallelBuilding = true;
   doCheck = true;
diff --git a/pkgs/tools/compression/zstd/default.nix b/pkgs/tools/compression/zstd/default.nix
index a014b652d313f..8cac630059244 100644
--- a/pkgs/tools/compression/zstd/default.nix
+++ b/pkgs/tools/compression/zstd/default.nix
@@ -13,7 +13,8 @@
   enableStatic ? static,
   # these need to be ran on the host, thus disable when cross-compiling
   buildContrib ? stdenv.hostPlatform == stdenv.buildPlatform,
-  doCheck ? stdenv.hostPlatform == stdenv.buildPlatform,
+  # permissions tests are currently failing on cygwin
+  doCheck ? stdenv.hostPlatform == stdenv.buildPlatform && !stdenv.buildPlatform.isCygwin,
   nix-update-script,
 
   # for passthru.tests
@@ -56,15 +57,23 @@ stdenv.mkDerivation (finalAttrs: {
     })
   ];
 
-  postPatch = lib.optionalString (!static) ''
-    substituteInPlace build/cmake/CMakeLists.txt \
-      --replace 'message(SEND_ERROR "You need to build static library to build tests")' ""
-    substituteInPlace build/cmake/tests/CMakeLists.txt \
-      --replace 'libzstd_static' 'libzstd_shared'
-    sed -i \
-      "1aexport ${lib.optionalString stdenv.hostPlatform.isDarwin "DY"}LD_LIBRARY_PATH=$PWD/build_/lib" \
-      tests/playTests.sh
-  '';
+  postPatch =
+    let
+      libPath =
+        if stdenv.hostPlatform.isCygwin then
+          "PATH=$PWD/build_/lib:$PATH"
+        else
+          "${lib.optionalString stdenv.hostPlatform.isDarwin "DY"}LD_LIBRARY_PATH=$PWD/build_/lib";
+    in
+    lib.optionalString (!static) ''
+      substituteInPlace build/cmake/CMakeLists.txt \
+        --replace 'message(SEND_ERROR "You need to build static library to build tests")' ""
+      substituteInPlace build/cmake/tests/CMakeLists.txt \
+        --replace 'libzstd_static' 'libzstd_shared'
+      sed -i \
+        "1aexport ${libPath}" \
+        tests/playTests.sh
+    '';
 
   cmakeFlags =
     lib.attrsets.mapAttrsToList (name: value: "-DZSTD_${name}:BOOL=${if value then "ON" else "OFF"}")
diff --git a/pkgs/tools/misc/findutils/default.nix b/pkgs/tools/misc/findutils/default.nix
index a5e8459355ac9..9a89b54c30d4a 100644
--- a/pkgs/tools/misc/findutils/default.nix
+++ b/pkgs/tools/misc/findutils/default.nix
@@ -22,6 +22,10 @@ stdenv.mkDerivation (finalAttrs: {
 
   postPatch = ''
     substituteInPlace xargs/xargs.c --replace 'char default_cmd[] = "echo";' 'char default_cmd[] = "${coreutils}/bin/echo";'
+  ''
+  # on cygwin, ARG_MAX is a low value which only applies to executing non-cygwin processes
+  + lib.optionalString stdenv.hostPlatform.isCygwin ''
+    substituteInPlace lib/buildcmd.c --replace-fail '#ifdef ARG_MAX' '#if 0'
   '';
 
   patches = [
@@ -40,6 +44,11 @@ stdenv.mkDerivation (finalAttrs: {
   doCheck =
     !stdenv.hostPlatform.isDarwin
     && !stdenv.hostPlatform.isFreeBSD
+    # FAIL: tests/find/depth-unreadable-dir.sh
+    # FAIL: tests/find/used.sh
+    # FAIL: tests/find/newer.sh
+    # FAIL: tests/find/type_list.sh
+    && !stdenv.hostPlatform.isCygwin
     && !(stdenv.hostPlatform.libc == "glibc" && stdenv.hostPlatform.isi686)
     && (stdenv.hostPlatform.libc != "musl")
     && stdenv.hostPlatform == stdenv.buildPlatform;
diff --git a/pkgs/tools/networking/openssh/common.nix b/pkgs/tools/networking/openssh/common.nix
index bafb82fa50909..e145b41730cf5 100644
--- a/pkgs/tools/networking/openssh/common.nix
+++ b/pkgs/tools/networking/openssh/common.nix
@@ -36,6 +36,7 @@
   libfido2,
   libxcrypt,
   hostname,
+  cygwin,
   nixosTests,
   withSecurityKey ? !stdenv.hostPlatform.isStatic,
   withFIDO ? stdenv.hostPlatform.isUnix && !stdenv.hostPlatform.isMusl && withSecurityKey,
@@ -109,6 +110,11 @@ stdenv.mkDerivation (finalAttrs: {
     # and nix store doesn't allow such fancy permission bits anyway.
     ''
       substituteInPlace Makefile.in --replace-fail '$(INSTALL) -m 4711' '$(INSTALL) -m 0711'
+    ''
+    + lib.optionalString stdenv.hostPlatform.isCygwin ''
+      substituteInPlace configure.ac --replace-fail \
+        '/usr/lib/textreadmode.o' \
+        '${lib.getLib cygwin.newlib-cygwin}/lib/textreadmode.o'
     '';
 
   strictDeps = true;
@@ -194,8 +200,11 @@ stdenv.mkDerivation (finalAttrs: {
     openssl
   ]
   ++ lib.optional (!stdenv.hostPlatform.isDarwin) hostname
-  ++ lib.optional (!stdenv.hostPlatform.isDarwin && !stdenv.hostPlatform.isMusl) softhsm;
+  ++ lib.optional (
+    !stdenv.hostPlatform.isDarwin && !stdenv.hostPlatform.isMusl && !stdenv.hostPlatform.isCygwin
+  ) softhsm;
 
+  # TODO: remove this when doCheck = false?
   preCheck = lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) (
     ''
       # construct a dummy HOME
@@ -213,7 +222,9 @@ stdenv.mkDerivation (finalAttrs: {
       # invoked directly and those invoked by the "remote" session
       cat > ~/.ssh/environment.base <<EOF
       NIX_REDIRECTS=/etc/passwd=$DUMMY_PASSWD
-      ${lib.optionalString (!stdenv.hostPlatform.isStatic) "LD_PRELOAD=${libredirect}/lib/libredirect.so"}
+      ${lib.optionalString (
+        !stdenv.hostPlatform.isStatic && !stdenv.buildPlatform.isCygwin
+      ) "LD_PRELOAD=${libredirect}/lib/libredirect.so"}
       EOF
 
       # use an ssh environment file to ensure environment is set
@@ -241,11 +252,20 @@ stdenv.mkDerivation (finalAttrs: {
       # set up NIX_REDIRECTS for direct invocations
       set -a; source ~/.ssh/environment.base; set +a
     ''
-    + lib.optionalString (!stdenv.hostPlatform.isDarwin && !stdenv.hostPlatform.isMusl) ''
-      # The extra tests check PKCS#11 interactions, which softhsm emulates with software only
-      substituteInPlace regress/test-exec.sh \
-        --replace-fail /usr/local/lib/softhsm/libsofthsm2.so ${lib.getLib softhsm}/lib/softhsm/libsofthsm2.so
-    ''
+    # See softhsm in nativeCheckInputs above.
+    +
+      lib.optionalString
+        (
+          !finalAttrs.doCheck
+          && !stdenv.hostPlatform.isDarwin
+          && !stdenv.hostPlatform.isMusl
+          && !stdenv.hostPlatform.isCygwin
+        )
+        ''
+          # The extra tests check PKCS#11 interactions, which softhsm emulates with software only
+          substituteInPlace regress/test-exec.sh \
+            --replace-fail /usr/local/lib/softhsm/libsofthsm2.so ${lib.getLib softhsm}/lib/softhsm/libsofthsm2.so
+        ''
   );
   # integration tests hard to get working on darwin with its shaky
   # sandbox
diff --git a/pkgs/tools/package-management/nix/modular/packaging/components.nix b/pkgs/tools/package-management/nix/modular/packaging/components.nix
index 02b927df5a23f..21bf2de14edbe 100644
--- a/pkgs/tools/package-management/nix/modular/packaging/components.nix
+++ b/pkgs/tools/package-management/nix/modular/packaging/components.nix
@@ -277,7 +277,14 @@ in
         /**
           Patches for the whole Nix source. Changes to packaging expressions will be ignored.
         */
-        patches = [ ];
+        patches = lib.optionals stdenv.hostPlatform.isCygwin [
+          ../../patches/Include-bin-in-builder-PATH-on-cygwin.patch
+          ../../patches/Suppress-xattr-errors-on-Cygwin.patch
+          ../../patches/Recreate-symlinks-on-cygwin.patch
+          ../../patches/libutil-tests-fix-openFileEnsureBeneathNoSymlinks.wo.patch
+          ../../patches/Fix-leak-in-EvalState-evalFile.patch
+          ../../patches/libflake-tests-fix-leak-in-nix_api_store_test.nix_ap.patch
+        ];
         /**
           Fetched and patched source to be used in component derivations.
         */
diff --git a/pkgs/tools/package-management/nix/modular/packaging/everything.nix b/pkgs/tools/package-management/nix/modular/packaging/everything.nix
index 62873710bcf39..f37bbc87eab1d 100644
--- a/pkgs/tools/package-management/nix/modular/packaging/everything.nix
+++ b/pkgs/tools/package-management/nix/modular/packaging/everything.nix
@@ -46,6 +46,8 @@
   testers,
 
   patchedSrc ? null,
+
+  enableDocumentation ? !stdenv.buildPlatform.isCygwin,
 }:
 
 let
@@ -106,6 +108,8 @@ stdenv.mkDerivation (finalAttrs: {
   outputs = [
     "out"
     "dev"
+  ]
+  ++ lib.optionals enableDocumentation [
     "doc"
     "man"
   ];
@@ -141,9 +145,9 @@ stdenv.mkDerivation (finalAttrs: {
     nix-fetchers-tests.tests.run
     nix-flake-tests.tests.run
 
-    # Make sure the functional tests have passed
-    nix-functional-tests
   ]
+  # Make sure the functional tests have passed
+  ++ lib.optional (!stdenv.buildPlatform.isCygwin) nix-functional-tests
   ++
     lib.optionals (!stdenv.hostPlatform.isStatic && stdenv.buildPlatform.canExecute stdenv.hostPlatform)
       [
@@ -173,6 +177,8 @@ stdenv.mkDerivation (finalAttrs: {
       for lib in ${lib.escapeShellArgs devPaths}; do
         lndir $lib $dev
       done
+    ''
+    + lib.optionalString enableDocumentation ''
 
       # Forwarded outputs
       ln -sT ${nix-manual} $doc
@@ -231,8 +237,8 @@ stdenv.mkDerivation (finalAttrs: {
     platforms = nix-cli.meta.platforms;
     outputsToInstall = [
       "out"
-      "man"
-    ];
+    ]
+    ++ lib.optional enableDocumentation "man";
     pkgConfigModules = [
       "nix-cmd"
       "nix-expr"
diff --git a/pkgs/tools/package-management/nix/modular/src/libexpr-tests/package.nix b/pkgs/tools/package-management/nix/modular/src/libexpr-tests/package.nix
index 1d5c729287788..02809a64588a5 100644
--- a/pkgs/tools/package-management/nix/modular/src/libexpr-tests/package.nix
+++ b/pkgs/tools/package-management/nix/modular/src/libexpr-tests/package.nix
@@ -43,7 +43,7 @@ mkMesonExecutable (finalAttrs: {
             meta.broken = !stdenv.hostPlatform.emulatorAvailable buildPackages;
           }
           (
-            lib.optionalString stdenv.hostPlatform.isWindows ''
+            lib.optionalString (stdenv.hostPlatform.isWindows || stdenv.hostPlatform.isCygwin) ''
               export HOME="$PWD/home-dir"
               mkdir -p "$HOME"
             ''
diff --git a/pkgs/tools/package-management/nix/modular/src/libstore/package.nix b/pkgs/tools/package-management/nix/modular/src/libstore/package.nix
index 6c5978bfd7e88..3039120e37dc2 100644
--- a/pkgs/tools/package-management/nix/modular/src/libstore/package.nix
+++ b/pkgs/tools/package-management/nix/modular/src/libstore/package.nix
@@ -25,7 +25,8 @@
 
   withAWS ?
     # Default is this way because there have been issues building this dependency
-    lib.meta.availableOn stdenv.hostPlatform aws-c-common,
+    # TODO: aws-crt-cpp is broken on cygwin, find a good way to check that here
+    lib.meta.availableOn stdenv.hostPlatform aws-c-common && !stdenv.hostPlatform.isCygwin,
 }:
 
 mkMesonLibrary (finalAttrs: {
diff --git a/pkgs/tools/package-management/nix/modular/src/perl/package.nix b/pkgs/tools/package-management/nix/modular/src/perl/package.nix
index d769d45d0f59a..1f348cb78a330 100644
--- a/pkgs/tools/package-management/nix/modular/src/perl/package.nix
+++ b/pkgs/tools/package-management/nix/modular/src/perl/package.nix
@@ -29,7 +29,19 @@ perl.pkgs.toPerlModule (
       nix-store
       bzip2
       libsodium
-    ];
+    ]
+    ++ lib.optional stdenv.hostPlatform.isCygwin perl;
+
+    env = lib.optionalAttrs stdenv.hostPlatform.isCygwin {
+      NIX_CFLAGS_COMPILE = toString (
+        lib.optionals stdenv.hostPlatform.isCygwin [
+          # longjmp, siginfo_t
+          "-D_POSIX_C_SOURCE=199309L"
+          # putenv
+          "-D_XOPEN_SOURCE"
+        ]
+      );
+    };
 
     # `perlPackages.Test2Harness` is marked broken for Darwin
     doCheck = !stdenv.isDarwin;
diff --git a/pkgs/tools/package-management/nix/patches/Disable-MonitorFdHup-test-on-cygwin.patch b/pkgs/tools/package-management/nix/patches/Disable-MonitorFdHup-test-on-cygwin.patch
new file mode 100644
index 0000000000000..f245833c509c6
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/Disable-MonitorFdHup-test-on-cygwin.patch
@@ -0,0 +1,23 @@
+From 48620255d396771e6da6458b77f2a438bf289ee7 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Sat, 15 Nov 2025 20:12:15 -0400
+Subject: [PATCH] Disable MonitorFdHup test on cygwin
+
+---
+ src/libutil-tests/monitorfdhup.cc | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/src/libutil-tests/monitorfdhup.cc b/src/libutil-tests/monitorfdhup.cc
+index d591b2fed..02cd7e22c 100644
+--- a/src/libutil-tests/monitorfdhup.cc
++++ b/src/libutil-tests/monitorfdhup.cc
+@@ -1,4 +1,5 @@
+-#ifndef _WIN32
++// TODO: investigate why this is hanging on cygwin
++#if !defined(_WIN32) && !defined(__CYGWIN__)
+ 
+ #  include "nix/util/util.hh"
+ #  include "nix/util/monitor-fd.hh"
+-- 
+2.51.0
+
diff --git a/pkgs/tools/package-management/nix/patches/Fix-leak-in-EvalState-evalFile.patch b/pkgs/tools/package-management/nix/patches/Fix-leak-in-EvalState-evalFile.patch
new file mode 100644
index 0000000000000..04203c365333d
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/Fix-leak-in-EvalState-evalFile.patch
@@ -0,0 +1,56 @@
+From 868b29c39a7c2e2dd8722a9e7208f193779a9e05 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Fri, 9 Jan 2026 15:53:46 -0400
+Subject: [PATCH] Fix leak in EvalState::evalFile
+
+---
+ src/libexpr/eval.cc                  | 4 ++--
+ src/libexpr/include/nix/expr/eval.hh | 4 ++++
+ 2 files changed, 6 insertions(+), 2 deletions(-)
+
+diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
+index 84f14198f..40f0b4b7b 100644
+--- a/src/libexpr/eval.cc
++++ b/src/libexpr/eval.cc
+@@ -1129,14 +1129,14 @@ void EvalState::evalFile(const SourcePath & path, Value & v, bool mustBeTrivial)
+     // https://github.com/NixOS/nix/pull/13930 is merged. That will ensure
+     // the post-condition that `expr` is unreachable after
+     // `forceValue()` returns.
+-    auto expr = new ExprParseFile{*resolvedPath, mustBeTrivial};
++    auto expr = parseFileExprs.emplace_back(std::make_shared<ExprParseFile>(*resolvedPath, mustBeTrivial));
+ 
+     fileEvalCache->try_emplace_and_cvisit(
+         *resolvedPath,
+         nullptr,
+         [&](auto & i) {
+             vExpr = allocValue();
+-            vExpr->mkThunk(&baseEnv, expr);
++            vExpr->mkThunk(&baseEnv, expr.get());
+             i.second = vExpr;
+         },
+         [&](auto & i) { vExpr = i.second; });
+diff --git a/src/libexpr/include/nix/expr/eval.hh b/src/libexpr/include/nix/expr/eval.hh
+index b70c9db78..ae6e32505 100644
+--- a/src/libexpr/include/nix/expr/eval.hh
++++ b/src/libexpr/include/nix/expr/eval.hh
+@@ -366,6 +366,8 @@ private:
+     Statistics stats;
+ };
+ 
++struct ExprParseFile;
++
+ class EvalState : public std::enable_shared_from_this<EvalState>
+ {
+ public:
+@@ -508,6 +510,8 @@ private:
+      */
+     const ref<RegexCache> regexCache;
+ 
++    std::vector<std::shared_ptr<ExprParseFile> > parseFileExprs;
++
+ public:
+ 
+     /**
+-- 
+2.52.0
+
diff --git a/pkgs/tools/package-management/nix/patches/Fix-leaks-in-nix_api_store_test.nix_eval_state_looku.patch b/pkgs/tools/package-management/nix/patches/Fix-leaks-in-nix_api_store_test.nix_eval_state_looku.patch
new file mode 100644
index 0000000000000..25f031351af52
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/Fix-leaks-in-nix_api_store_test.nix_eval_state_looku.patch
@@ -0,0 +1,33 @@
+From eaadc7eb7cf0efb16b388592d598bb5569214b47 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Sat, 15 Nov 2025 15:35:02 -0400
+Subject: [PATCH] Fix leaks in nix_api_store_test.nix_eval_state_lookup_path
+
+---
+ src/libexpr-tests/nix_api_expr.cc | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/src/libexpr-tests/nix_api_expr.cc b/src/libexpr-tests/nix_api_expr.cc
+index 02f99675e..3e5cd0d43 100644
+--- a/src/libexpr-tests/nix_api_expr.cc
++++ b/src/libexpr-tests/nix_api_expr.cc
+@@ -42,12 +42,16 @@ TEST_F(nix_api_expr_test, nix_eval_state_lookup_path)
+     nix_expr_eval_from_string(ctx, state, "builtins.seq <nixos-config> <nixpkgs>", ".", value);
+     assert_ctx_ok();
+ 
++    nix_state_free(state);
++
+     ASSERT_EQ(nix_get_type(ctx, value), NIX_TYPE_PATH);
+     assert_ctx_ok();
+ 
+     auto pathStr = nix_get_path_string(ctx, value);
+     assert_ctx_ok();
+     ASSERT_EQ(0, strcmp(pathStr, nixpkgs.c_str()));
++
++    nix_gc_decref(nullptr, value);
+ }
+ 
+ TEST_F(nix_api_expr_test, nix_expr_eval_from_string)
+-- 
+2.51.0
+
diff --git a/pkgs/tools/package-management/nix/patches/Fix-nix_api_store_test.nix_eval_state_lookup_path-wh.patch b/pkgs/tools/package-management/nix/patches/Fix-nix_api_store_test.nix_eval_state_lookup_path-wh.patch
new file mode 100644
index 0000000000000..40e5e8cf3bbc3
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/Fix-nix_api_store_test.nix_eval_state_lookup_path-wh.patch
@@ -0,0 +1,34 @@
+From c5f0d294e5c21ef333b4cd1e5d0135acd8398c24 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Sat, 15 Nov 2025 14:02:35 -0400
+Subject: [PATCH 1/2] Fix nix_api_store_test.nix_eval_state_lookup_path when
+ run on its own
+
+Currently, --gtest_filter=nix_api_store_test.nix_eval_state_lookup_path
+will result in:
+
+ terminating due to unexpected unrecoverable internal error: Assertion
+ 'gcInitialised' failed in void nix::assertGCInitialized() at
+ ../src/libexpr/eval-gc.cc:138
+
+Changing the test fixture to _exr_test causes GC to be initialised.
+---
+ src/libexpr-tests/nix_api_expr.cc | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/libexpr-tests/nix_api_expr.cc b/src/libexpr-tests/nix_api_expr.cc
+index de508b4e4..02f99675e 100644
+--- a/src/libexpr-tests/nix_api_expr.cc
++++ b/src/libexpr-tests/nix_api_expr.cc
+@@ -14,7 +14,7 @@
+ 
+ namespace nixC {
+ 
+-TEST_F(nix_api_store_test, nix_eval_state_lookup_path)
++TEST_F(nix_api_expr_test, nix_eval_state_lookup_path)
+ {
+     auto tmpDir = nix::createTempDir();
+     auto delTmpDir = std::make_unique<nix::AutoDelete>(tmpDir, true);
+-- 
+2.51.0
+
diff --git a/pkgs/tools/package-management/nix/patches/Fix-toString-ToStringPrimOpTest.toString-10-on-cygwi.patch b/pkgs/tools/package-management/nix/patches/Fix-toString-ToStringPrimOpTest.toString-10-on-cygwi.patch
new file mode 100644
index 0000000000000..70894c49b3c41
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/Fix-toString-ToStringPrimOpTest.toString-10-on-cygwi.patch
@@ -0,0 +1,30 @@
+From a91a74b3dbbb5cd9e9372b99694e5bdc83c648bd Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Sat, 15 Nov 2025 17:10:21 -0400
+Subject: [PATCH] Fix toString/ToStringPrimOpTest.toString/10 on cygwin
+
+---
+ src/libexpr-tests/primops.cc | 7 ++++++-
+ 1 file changed, 6 insertions(+), 1 deletion(-)
+
+diff --git a/src/libexpr-tests/primops.cc b/src/libexpr-tests/primops.cc
+index f00b4f475..48f9aee72 100644
+--- a/src/libexpr-tests/primops.cc
++++ b/src/libexpr-tests/primops.cc
+@@ -662,7 +662,12 @@ INSTANTIATE_TEST_SUITE_P(
+         CASE(R"({ v = "bar"; __toString = self: self.v; })", "bar"),
+         CASE(R"({ v = "bar"; __toString = self: self.v; outPath = "foo"; })", "bar"),
+         CASE(R"({ outPath = "foo"; })", "foo"),
+-        CASE(R"(./test)", "/test")));
++        CASE(R"(./test)",
++// canonPath("//./test", false) on cygwin returns //./test
++#ifdef __CYGWIN__
++            "//."
++#endif
++            "/test")));
+ #undef CASE
+ 
+ TEST_F(PrimOpTest, substring)
+-- 
+2.51.0
+
diff --git a/pkgs/tools/package-management/nix/patches/Include-bin-in-builder-PATH-on-cygwin.patch b/pkgs/tools/package-management/nix/patches/Include-bin-in-builder-PATH-on-cygwin.patch
new file mode 100644
index 0000000000000..1b54a1f555ec6
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/Include-bin-in-builder-PATH-on-cygwin.patch
@@ -0,0 +1,32 @@
+From b64bfd3db32542324cc724fc8b2a6e36bf856f47 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Wed, 1 Oct 2025 13:36:33 -0300
+Subject: [PATCH] Include /bin in builder PATH on cygwin
+
+---
+ src/libstore/unix/build/derivation-builder.cc | 9 ++++++++-
+ 1 file changed, 8 insertions(+), 1 deletion(-)
+
+diff --git a/src/libstore/unix/build/derivation-builder.cc b/src/libstore/unix/build/derivation-builder.cc
+index f94bb40cc..d817f954d 100644
+--- a/src/libstore/unix/build/derivation-builder.cc
++++ b/src/libstore/unix/build/derivation-builder.cc
+@@ -981,7 +981,14 @@ void DerivationBuilderImpl::initEnv()
+     /* Most shells initialise PATH to some default (/bin:/usr/bin:...) when
+        PATH is not set.  We don't want this, so we fill it in with some dummy
+        value. */
+-    env["PATH"] = "/path-not-set";
++    env["PATH"] =
++#ifdef __CYGWIN__
++        // on cygwin we always need /bin in PATH, so cygwin1.dll can be found
++        "/bin"
++#else
++        "/path-not-set"
++#endif
++        ;
+ 
+     /* Set HOME to a non-existing path to prevent certain programs from using
+        /etc/passwd (or NIS, or whatever) to locate the home directory (for
+-- 
+2.51.0
+
diff --git a/pkgs/tools/package-management/nix/patches/Recreate-symlinks-on-cygwin.patch b/pkgs/tools/package-management/nix/patches/Recreate-symlinks-on-cygwin.patch
new file mode 100644
index 0000000000000..93737739b7b2a
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/Recreate-symlinks-on-cygwin.patch
@@ -0,0 +1,79 @@
+From 501ecb34ff06f4fedd900e661a46c294c2a90e02 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Fri, 26 Dec 2025 15:04:26 -0400
+Subject: [PATCH] Recreate symlinks on cygwin
+
+---
+ src/libstore/posix-fs-canonicalise.cc | 28 +++++++++++++++++++++++++--
+ 1 file changed, 26 insertions(+), 2 deletions(-)
+
+diff --git a/src/libstore/posix-fs-canonicalise.cc b/src/libstore/posix-fs-canonicalise.cc
+index 7c7a60e87..1a00999a3 100644
+--- a/src/libstore/posix-fs-canonicalise.cc
++++ b/src/libstore/posix-fs-canonicalise.cc
+@@ -15,6 +15,18 @@ namespace nix {
+ 
+ const time_t mtimeStore = 1; /* 1 second into the epoch */
+ 
++static void makeDirectoryWritable(const Path & path, const struct stat & st)
++{
++    if (!S_ISDIR(st.st_mode))
++        return;
++
++    mode_t mode = st.st_mode | 0220;
++    if (mode != st.st_mode) {
++        if (chmod(path.c_str(), mode) == -1)
++            throw SysError("changing mode of '%1%' to %2$o", path, mode);
++    }
++}
++
+ static void canonicaliseTimestampAndPermissions(const Path & path, const struct stat & st)
+ {
+     if (!S_ISLNK(st.st_mode)) {
+@@ -63,6 +75,14 @@ static void canonicalisePathMetaData_(
+ 
+     auto st = lstat(path);
+ 
++#if __CYGWIN__
++    // replace all symlinks to ensure native symlinks can be created
++    if (S_ISLNK(st.st_mode)) {
++        auto target = readLink(path);
++        replaceSymlink(target, path);
++    }
++#endif
++
+     /* Really make sure that the path is of a supported type. */
+     if (!(S_ISREG(st.st_mode) || S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode)))
+         throw Error("file '%1%' has an unsupported type", path);
+@@ -114,8 +134,6 @@ static void canonicalisePathMetaData_(
+ 
+     inodesSeen.insert(Inode(st.st_dev, st.st_ino));
+ 
+-    canonicaliseTimestampAndPermissions(path, st);
+-
+ #ifndef _WIN32
+     /* Change ownership to the current uid.  If it's a symlink, use
+        lchown if available, otherwise don't bother.  Wrong ownership
+@@ -134,6 +152,10 @@ static void canonicalisePathMetaData_(
+     }
+ #endif
+ 
++#if __CYGWIN__
++    makeDirectoryWritable(path, st);
++#endif
++
+     if (S_ISDIR(st.st_mode)) {
+         for (auto & i : DirectoryIterator{path}) {
+             checkInterrupt();
+@@ -145,6 +167,8 @@ static void canonicalisePathMetaData_(
+                 inodesSeen);
+         }
+     }
++
++    canonicaliseTimestampAndPermissions(path, st);
+ }
+ 
+ void canonicalisePathMetaData(
+-- 
+2.51.2
+
diff --git a/pkgs/tools/package-management/nix/patches/Remove-static-data-from-headers.patch b/pkgs/tools/package-management/nix/patches/Remove-static-data-from-headers.patch
new file mode 100644
index 0000000000000..83f87646ca3b7
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/Remove-static-data-from-headers.patch
@@ -0,0 +1,203 @@
+From 1b5af49fd0e3bc9c047054bd95c1c749d10b8d7c Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Wed, 12 Nov 2025 19:52:29 -0400
+Subject: [PATCH] Remove static data from headers
+
+We don't want to duplicate any of these across libraries, which is what
+happens when the platform doesn't support unique symbols.
+---
+ src/libcmd/command.cc                         | 13 +++++++++++++
+ src/libcmd/include/nix/cmd/command.hh         |  6 +-----
+ src/libcmd/include/nix/cmd/legacy.hh          |  6 +-----
+ src/libexpr/include/nix/expr/primops.hh       |  6 +-----
+ src/libexpr/include/nix/expr/print-options.hh |  2 +-
+ src/libexpr/primops.cc                        |  6 ++++++
+ src/libstore/builtins/buildenv.cc             |  6 ++++++
+ src/libstore/include/nix/store/builtins.hh    |  6 +-----
+ src/libutil/config-global.cc                  |  6 ++++++
+ src/libutil/include/nix/util/config-global.hh |  6 +-----
+ 10 files changed, 37 insertions(+), 26 deletions(-)
+
+diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
+index 6b6bbe345..b06d40902 100644
+--- a/src/libcmd/command.cc
++++ b/src/libcmd/command.cc
+@@ -2,6 +2,7 @@
+ #include <nlohmann/json.hpp>
+ 
+ #include "nix/cmd/command.hh"
++#include "nix/cmd/legacy.hh"
+ #include "nix/cmd/markdown.hh"
+ #include "nix/store/store-open.hh"
+ #include "nix/store/local-fs-store.hh"
+@@ -14,6 +15,18 @@
+ 
+ namespace nix {
+ 
++RegisterCommand::Commands & RegisterCommand::commands()
++{
++    static RegisterCommand::Commands commands;
++    return commands;
++}
++
++RegisterLegacyCommand::Commands & RegisterLegacyCommand::commands()
++{
++    static RegisterLegacyCommand::Commands commands;
++    return commands;
++}
++
+ nix::Commands RegisterCommand::getCommandsFor(const std::vector<std::string> & prefix)
+ {
+     nix::Commands res;
+diff --git a/src/libcmd/include/nix/cmd/command.hh b/src/libcmd/include/nix/cmd/command.hh
+index 2bff11dc1..2f97b30da 100644
+--- a/src/libcmd/include/nix/cmd/command.hh
++++ b/src/libcmd/include/nix/cmd/command.hh
+@@ -286,11 +286,7 @@ struct RegisterCommand
+ {
+     typedef std::map<std::vector<std::string>, std::function<ref<Command>()>> Commands;
+ 
+-    static Commands & commands()
+-    {
+-        static Commands commands;
+-        return commands;
+-    }
++    static Commands & commands();
+ 
+     RegisterCommand(std::vector<std::string> && name, std::function<ref<Command>()> command)
+     {
+diff --git a/src/libcmd/include/nix/cmd/legacy.hh b/src/libcmd/include/nix/cmd/legacy.hh
+index 546057184..d408cde7a 100644
+--- a/src/libcmd/include/nix/cmd/legacy.hh
++++ b/src/libcmd/include/nix/cmd/legacy.hh
+@@ -13,11 +13,7 @@ struct RegisterLegacyCommand
+ {
+     typedef std::map<std::string, MainFunction> Commands;
+ 
+-    static Commands & commands()
+-    {
+-        static Commands commands;
+-        return commands;
+-    }
++    static Commands & commands();
+ 
+     RegisterLegacyCommand(const std::string & name, MainFunction fun)
+     {
+diff --git a/src/libexpr/include/nix/expr/primops.hh b/src/libexpr/include/nix/expr/primops.hh
+index 6407ba84e..8854f6b03 100644
+--- a/src/libexpr/include/nix/expr/primops.hh
++++ b/src/libexpr/include/nix/expr/primops.hh
+@@ -12,11 +12,7 @@ struct RegisterPrimOp
+ {
+     typedef std::vector<PrimOp> PrimOps;
+ 
+-    static PrimOps & primOps()
+-    {
+-        static PrimOps primOps;
+-        return primOps;
+-    }
++    static PrimOps & primOps();
+ 
+     /**
+      * You can register a constant by passing an arity of 0. fun
+diff --git a/src/libexpr/include/nix/expr/print-options.hh b/src/libexpr/include/nix/expr/print-options.hh
+index ffb80abc3..600b96ba2 100644
+--- a/src/libexpr/include/nix/expr/print-options.hh
++++ b/src/libexpr/include/nix/expr/print-options.hh
+@@ -110,7 +110,7 @@ struct PrintOptions
+  * `PrintOptions` for unknown and therefore potentially large values in error messages,
+  * to avoid printing "too much" output.
+  */
+-static PrintOptions errorPrintOptions = PrintOptions{
++static constexpr PrintOptions errorPrintOptions = PrintOptions{
+     .ansiColors = true,
+     .maxDepth = 10,
+     .maxAttrs = 10,
+diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
+index 98ed1b450..35f16a68d 100644
+--- a/src/libexpr/primops.cc
++++ b/src/libexpr/primops.cc
+@@ -40,6 +40,12 @@
+ 
+ namespace nix {
+ 
++RegisterPrimOp::PrimOps & RegisterPrimOp::primOps()
++{
++    static RegisterPrimOp::PrimOps primOps;
++    return primOps;
++}
++
+ /*************************************************************
+  * Miscellaneous
+  *************************************************************/
+diff --git a/src/libstore/builtins/buildenv.cc b/src/libstore/builtins/buildenv.cc
+index 22ed8d807..4db37d43a 100644
+--- a/src/libstore/builtins/buildenv.cc
++++ b/src/libstore/builtins/buildenv.cc
+@@ -10,6 +10,12 @@
+ 
+ namespace nix {
+ 
++RegisterBuiltinBuilder::BuiltinBuilders & RegisterBuiltinBuilder::builtinBuilders()
++{
++    static RegisterBuiltinBuilder::BuiltinBuilders builders;
++    return builders;
++}
++
+ namespace {
+ 
+ struct State
+diff --git a/src/libstore/include/nix/store/builtins.hh b/src/libstore/include/nix/store/builtins.hh
+index 6925e61c1..7cc9c0911 100644
+--- a/src/libstore/include/nix/store/builtins.hh
++++ b/src/libstore/include/nix/store/builtins.hh
+@@ -33,11 +33,7 @@ struct RegisterBuiltinBuilder
+ {
+     typedef std::map<std::string, BuiltinBuilder> BuiltinBuilders;
+ 
+-    static BuiltinBuilders & builtinBuilders()
+-    {
+-        static BuiltinBuilders builders;
+-        return builders;
+-    }
++    static BuiltinBuilders & builtinBuilders();
+ 
+     RegisterBuiltinBuilder(const std::string & name, BuiltinBuilder && fun)
+     {
+diff --git a/src/libutil/config-global.cc b/src/libutil/config-global.cc
+index cd461ea48..b63b4aaa1 100644
+--- a/src/libutil/config-global.cc
++++ b/src/libutil/config-global.cc
+@@ -4,6 +4,12 @@
+ 
+ namespace nix {
+ 
++GlobalConfig::ConfigRegistrations & GlobalConfig::configRegistrations()
++{
++    static GlobalConfig::ConfigRegistrations configRegistrations;
++    return configRegistrations;
++}
++
+ bool GlobalConfig::set(const std::string & name, const std::string & value)
+ {
+     for (auto & config : configRegistrations())
+diff --git a/src/libutil/include/nix/util/config-global.hh b/src/libutil/include/nix/util/config-global.hh
+index 0e6f43ec4..5074351e0 100644
+--- a/src/libutil/include/nix/util/config-global.hh
++++ b/src/libutil/include/nix/util/config-global.hh
+@@ -9,11 +9,7 @@ struct GlobalConfig : public AbstractConfig
+ {
+     typedef std::vector<Config *> ConfigRegistrations;
+ 
+-    static ConfigRegistrations & configRegistrations()
+-    {
+-        static ConfigRegistrations configRegistrations;
+-        return configRegistrations;
+-    }
++    static ConfigRegistrations & configRegistrations();
+ 
+     bool set(const std::string & name, const std::string & value) override;
+ 
+-- 
+2.51.0
+
diff --git a/pkgs/tools/package-management/nix/patches/Suppress-xattr-errors-on-Cygwin.patch b/pkgs/tools/package-management/nix/patches/Suppress-xattr-errors-on-Cygwin.patch
new file mode 100644
index 0000000000000..ae26910de1a6d
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/Suppress-xattr-errors-on-Cygwin.patch
@@ -0,0 +1,32 @@
+From ac7a7e37992c5fc37cca35abe8d3c17ada2fb810 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Wed, 3 Dec 2025 14:10:05 -0400
+Subject: [PATCH] Suppress xattr errors on Cygwin
+
+---
+ src/libstore/posix-fs-canonicalise.cc | 9 +++++++--
+ 1 file changed, 7 insertions(+), 2 deletions(-)
+
+diff --git a/src/libstore/posix-fs-canonicalise.cc b/src/libstore/posix-fs-canonicalise.cc
+index a274468c3..7c7a60e87 100644
+--- a/src/libstore/posix-fs-canonicalise.cc
++++ b/src/libstore/posix-fs-canonicalise.cc
+@@ -72,8 +72,13 @@ static void canonicalisePathMetaData_(
+     ssize_t eaSize = llistxattr(path.c_str(), nullptr, 0);
+ 
+     if (eaSize < 0) {
+-        if (errno != ENOTSUP && errno != ENODATA)
+-            throw SysError("querying extended attributes of '%s'", path);
++        if (errno != ENOTSUP && errno != ENODATA
++// Cygwin llistxattr currently returns EPERM for symbolic links
++#ifdef __CYGWIN__
++            && !(errno == EACCES && S_ISLNK(st.st_mode))
++#endif
++            )
++            throw SysError("querying extended attributes of '%s', %i, %i", path, (int)errno, (int)S_ISLNK(st.st_mode));
+     } else if (eaSize > 0) {
+         std::vector<char> eaBuf(eaSize);
+ 
+-- 
+2.51.2
+
diff --git a/pkgs/tools/package-management/nix/patches/fix-cygwin-build.patch b/pkgs/tools/package-management/nix/patches/fix-cygwin-build.patch
new file mode 100644
index 0000000000000..30e4e4cfc0717
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/fix-cygwin-build.patch
@@ -0,0 +1,35 @@
+diff --git a/src/libutil/unix/signals.cc b/src/libutil/unix/signals.cc
+index 8a94cc2..a73715e 100644
+--- a/src/libutil/unix/signals.cc
++++ b/src/libutil/unix/signals.cc
+@@ -103,8 +103,8 @@ void unix::setChildSignalMask(sigset_t * sigs)
+ {
+     assert(sigs); // C style function, but think of sigs as a reference
+ 
+-#if (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 1) || (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE) \
+-    || (defined(_POSIX_SOURCE) && _POSIX_SOURCE)
++#if ((defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 1) || (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE) \
++    || (defined(_POSIX_SOURCE) && _POSIX_SOURCE)) && !defined(__CYGWIN__)
+     sigemptyset(&savedSignalMask);
+     // There's no "assign" or "copy" function, so we rely on (math) idempotence
+     // of the or operator: a or a = a.
+diff --git a/src/libstore/posix-fs-canonicalise.cc b/src/libstore/posix-fs-canonicalise.cc
+index 2484d51a6..6b759a406 100644
+--- a/src/libstore/posix-fs-canonicalise.cc
++++ b/src/libstore/posix-fs-canonicalise.cc
+@@ -72,8 +72,13 @@ static void canonicalisePathMetaData_(
+     ssize_t eaSize = llistxattr(path.c_str(), nullptr, 0);
+ 
+     if (eaSize < 0) {
+-        if (errno != ENOTSUP && errno != ENODATA)
+-            throw SysError("querying extended attributes of '%s'", path);
++        if (errno != ENOTSUP && errno != ENODATA
++// Cygwin llistxattr currently returns EPERM for symbolic links
++#ifdef __CYGWIN__
++            && !(errno == EACCES && S_ISLNK(st.st_mode))
++#endif
++            )
++            throw SysError("querying extended attributes of '%s', %i, %i", path, (int)errno, (int)S_ISLNK(st.st_mode));
+     } else if (eaSize > 0) {
+         std::vector<char> eaBuf(eaSize);
+ 
diff --git a/pkgs/tools/package-management/nix/patches/libflake-tests-fix-leak-in-nix_api_store_test.nix_ap.patch b/pkgs/tools/package-management/nix/patches/libflake-tests-fix-leak-in-nix_api_store_test.nix_ap.patch
new file mode 100644
index 0000000000000..cad2737ff8048
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/libflake-tests-fix-leak-in-nix_api_store_test.nix_ap.patch
@@ -0,0 +1,25 @@
+From 7fa550aac32900720af1004187b0a087eec8ce79 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Fri, 9 Jan 2026 16:27:19 -0400
+Subject: [PATCH] libflake-tests: fix leak in
+ nix_api_store_test.nix_api_load_flake_with_flags
+
+---
+ src/libflake-tests/nix_api_flake.cc | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/src/libflake-tests/nix_api_flake.cc b/src/libflake-tests/nix_api_flake.cc
+index 45f3d9b29..063dfc4d7 100644
+--- a/src/libflake-tests/nix_api_flake.cc
++++ b/src/libflake-tests/nix_api_flake.cc
+@@ -377,6 +377,7 @@ TEST_F(nix_api_store_test, nix_api_load_flake_with_flags)
+     assert_ctx_ok();
+     ASSERT_EQ("Claire", helloStr);
+ 
++    nix_locked_flake_free(lockedFlake);
+     nix_flake_reference_parse_flags_free(parseFlags);
+     nix_flake_lock_flags_free(lockFlags);
+     nix_flake_reference_free(flakeReference);
+-- 
+2.52.0
+
diff --git a/pkgs/tools/package-management/nix/patches/libutil-tests-fix-openFileEnsureBeneathNoSymlinks.wo.patch b/pkgs/tools/package-management/nix/patches/libutil-tests-fix-openFileEnsureBeneathNoSymlinks.wo.patch
new file mode 100644
index 0000000000000..da391086d4062
--- /dev/null
+++ b/pkgs/tools/package-management/nix/patches/libutil-tests-fix-openFileEnsureBeneathNoSymlinks.wo.patch
@@ -0,0 +1,32 @@
+From 88b985ab6857625e1f79df64f7b5b8bf6893239d Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Thu, 8 Jan 2026 13:27:55 -0400
+Subject: [PATCH] libutil-tests: fix openFileEnsureBeneathNoSymlinks.works on
+ cygwin
+
+---
+ src/libutil-tests/file-system.cc | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/src/libutil-tests/file-system.cc b/src/libutil-tests/file-system.cc
+index 1551227cb..3d1670813 100644
+--- a/src/libutil-tests/file-system.cc
++++ b/src/libutil-tests/file-system.cc
+@@ -369,9 +369,14 @@ TEST(openFileEnsureBeneathNoSymlinks, works)
+     EXPECT_THROW(open("a/absolute_symlink/c/d", O_RDONLY), SymlinkNotAllowed);
+     EXPECT_THROW(open("a/relative_symlink/c", O_RDONLY), SymlinkNotAllowed);
+     EXPECT_THROW(open("a/b/c/d", O_RDONLY), SymlinkNotAllowed);
++#ifdef __CYGWIN__
++    // this returns ELOOP on cygwin when O_NOFOLLOW is used
++    EXPECT_THROW(open("a/broken_symlink", O_CREAT | O_WRONLY | O_EXCL, 0666), SymlinkNotAllowed);
++#else
+     EXPECT_EQ(open("a/broken_symlink", O_CREAT | O_WRONLY | O_EXCL, 0666), INVALID_DESCRIPTOR);
+     /* Sanity check, no symlink shenanigans and behaves the same as regular openat with O_EXCL | O_CREAT. */
+     EXPECT_EQ(errno, EEXIST);
++#endif
+     EXPECT_THROW(open("a/absolute_symlink/broken_symlink", O_CREAT | O_WRONLY | O_EXCL, 0666), SymlinkNotAllowed);
+     EXPECT_EQ(open("c/d/regular/a", O_RDONLY), INVALID_DESCRIPTOR);
+     EXPECT_EQ(open("c/d/regular", O_RDONLY | O_DIRECTORY), INVALID_DESCRIPTOR);
+-- 
+2.52.0
+
diff --git a/pkgs/tools/text/gnupatch/default.nix b/pkgs/tools/text/gnupatch/default.nix
index ddb0914dbe842..4cd0dd23825a1 100644
--- a/pkgs/tools/text/gnupatch/default.nix
+++ b/pkgs/tools/text/gnupatch/default.nix
@@ -27,7 +27,7 @@ stdenv.mkDerivation (finalAttrs: {
     "ac_cv_func_strnlen_working=yes"
   ];
 
-  doCheck = stdenv.hostPlatform.libc != "musl"; # not cross;
+  doCheck = stdenv.hostPlatform.libc != "musl" && !stdenv.hostPlatform.isCygwin; # not cross;
   nativeCheckInputs = [ ed ];
 
   meta = {
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 6e6dd6fff9b5b..21444a8ec6418 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -611,7 +611,9 @@ with pkgs;
           # So turn gssSupport off there, and on Windows.
           # On other platforms, keep the previous value.
           gssSupport =
-            if stdenv.hostPlatform.isDarwin || stdenv.hostPlatform.isWindows then
+            if
+              stdenv.hostPlatform.isDarwin || stdenv.hostPlatform.isWindows || stdenv.hostPlatform.isCygwin
+            then
               false
             else
               old.gssSupport or true; # `? true` is the default
@@ -5116,8 +5118,10 @@ with pkgs;
     callPackage ../build-support/cc-wrapper (
       let
         self = {
-          nativeTools = stdenv.targetPlatform == stdenv.hostPlatform && stdenv.cc.nativeTools or false;
-          nativeLibc = stdenv.targetPlatform == stdenv.hostPlatform && stdenv.cc.nativeLibc or false;
+          nativeTools =
+            stdenv.targetPlatform == stdenv.hostPlatform && stdenv.cc.nativeTools or false && cc == null;
+          nativeLibc =
+            stdenv.targetPlatform == stdenv.hostPlatform && stdenv.cc.nativeLibc or false && libc == null;
           nativePrefix = stdenv.cc.nativePrefix or "";
           noLibc = !self.nativeLibc && (self.libc == null);
 
@@ -5155,8 +5159,10 @@ with pkgs;
     callPackage ../build-support/bintools-wrapper (
       let
         self = {
-          nativeTools = stdenv.targetPlatform == stdenv.hostPlatform && stdenv.cc.nativeTools or false;
-          nativeLibc = stdenv.targetPlatform == stdenv.hostPlatform && stdenv.cc.nativeLibc or false;
+          nativeTools =
+            stdenv.targetPlatform == stdenv.hostPlatform && stdenv.cc.nativeTools or false && bintools == null;
+          nativeLibc =
+            stdenv.targetPlatform == stdenv.hostPlatform && stdenv.cc.nativeLibc or false && libc == null;
           nativePrefix = stdenv.cc.nativePrefix or "";
 
           noLibc = (self.libc == null);
@@ -6845,7 +6851,7 @@ with pkgs;
     else if libc == "ucrt" then
       if stdenv.hostPlatform.isMinGW then windows.mingw_w64 else windows.sdk
     else if libc == "cygwin" then
-      cygwin.newlib-cygwin-nobin
+      cygwin.newlib-cygwin
     else if libc == "libSystem" then
       if stdenv.hostPlatform.useiOSPrebuilt then darwin.iosSdkPkgs.libraries else darwin.libSystem
     else if libc == "fblibc" then
diff --git a/pkgs/top-level/perl-packages.nix b/pkgs/top-level/perl-packages.nix
index 0110bcdeb1b19..46957c2f3bdee 100644
--- a/pkgs/top-level/perl-packages.nix
+++ b/pkgs/top-level/perl-packages.nix
@@ -25985,6 +25985,8 @@ with self;
       hash = "sha256-eynEWt0Z09UIS3Ufe6iajkBHmkRs4hz9nMdB5VgzKgA=";
     };
     propagatedBuildInputs = [ IOSocketSSL ];
+    # TODO: fix PATH needed for dependencies
+    doCheck = !stdenv.buildPlatform.isCygwin;
     meta = {
       description = "SSL support for Net::SMTP";
       license = with lib.licenses; [
@@ -33242,7 +33244,8 @@ with self;
 
     # The t/integration/preload.t test is broken on riscv64
     # https://github.com/Test-More/Test2-Harness/issues/290
-    doCheck = !stdenv.hostPlatform.isRiscV;
+    # There seems to be a similar failure on cygwin
+    doCheck = !stdenv.hostPlatform.isRiscV && !stdenv.buildPlatform.isCygwin;
 
     propagatedBuildInputs = [
       DataUUID
@@ -38666,18 +38669,18 @@ with self;
       url = "mirror://cpan/authors/id/T/TO/TODDR/XML-Parser-2.46.tar.gz";
       hash = "sha256-0zEzJJHFHMz7TLlP/ET5zXM3jmGEmNSjffngQ2YcUV0=";
     };
-    patches = [ ../development/perl-modules/xml-parser-0001-HACK-Assumes-Expat-paths-are-good.patch ];
-    postPatch =
-      lib.optionalString (stdenv.buildPlatform != stdenv.hostPlatform) ''
-        substituteInPlace Expat/Makefile.PL --replace 'use English;' '#'
-      ''
-      + lib.optionalString stdenv.hostPlatform.isCygwin ''
-        sed -i -e "s@my \$compiler = File::Spec->catfile(\$path, \$cc\[0\]) \. \$Config{_exe};@my \$compiler = File::Spec->catfile(\$path, \$cc\[0\]) \. (\$^O eq 'cygwin' ? \"\" : \$Config{_exe});@" inc/Devel/CheckLib.pm
-      '';
+    patches = [
+      ../development/perl-modules/xml-parser-0001-HACK-Assumes-Expat-paths-are-good.patch
+    ]
+    ++ lib.optional stdenv.buildPlatform.isCygwin ../development/perl-modules/cygwin-checklib-fix.patch;
+    postPatch = lib.optionalString (stdenv.buildPlatform != stdenv.hostPlatform) ''
+      substituteInPlace Expat/Makefile.PL --replace 'use English;' '#'
+    '';
     makeMakerFlags = [
       "EXPATLIBPATH=${pkgs.expat.out}/lib"
       "EXPATINCPATH=${pkgs.expat.dev}/include"
     ];
+    buildInputs = lib.optional stdenv.hostPlatform.isCygwin pkgs.expat;
     propagatedBuildInputs = [ LWP ];
     meta = {
       description = "Perl module for parsing XML documents";
diff --git a/pkgs/top-level/release-cross.nix b/pkgs/top-level/release-cross.nix
index 95d30e66077a4..4e393d821cd63 100644
--- a/pkgs/top-level/release-cross.nix
+++ b/pkgs/top-level/release-cross.nix
@@ -300,12 +300,16 @@ in
     let
       linuxTools = import ../stdenv/linux/make-bootstrap-tools-cross.nix { system = "x86_64-linux"; };
       freebsdTools = import ../stdenv/freebsd/make-bootstrap-tools-cross.nix { system = "x86_64-linux"; };
+      cygwinTools = import ../stdenv/cygwin/make-bootstrap-tools-cross.nix { system = "x86_64-linux"; };
       linuxMeta = {
         maintainers = [ maintainers.dezgeg ];
       };
       freebsdMeta = {
         maintainers = [ maintainers.rhelmot ];
       };
+      cygwinMeta = {
+        maintainers = [ maintainers.corngood ];
+      };
       mkBootstrapToolsJob =
         meta: drv:
         assert elem drv.system supportedSystems;
@@ -331,8 +335,11 @@ in
       freebsd = mapAttrsRecursiveCond (as: !isDerivation as) (
         name: mkBootstrapToolsJob freebsdMeta
       ) freebsdTools;
+      cygwin = mapAttrsRecursiveCond (as: !isDerivation as) (
+        name: mkBootstrapToolsJob cygwinMeta
+      ) cygwinTools;
     in
-    linux // freebsd;
+    linux // freebsd // cygwin;
 
   # Cross-built nixStatic for platforms for enabled-but-unsupported platforms
   mips64el-nixCrossStatic = mapTestOnCross systems.examples.mips64el-linux-gnuabi64 nixCrossStatic;