From cdd8dc5f47c3704ca851e66ac422053d6746d97c Mon Sep 17 00:00:00 2001
From: Daniel Kraus <daniel@kraus.my>
Date: Tue, 14 Jul 2026 09:56:31 +0200
Subject: [PATCH] Require exactly Zig 0.15.2 to build the native module

A minimum_zig_version in build.zig.zon rejects older Zig before the
build script compiles, and a comptime guard in build.zig rejects any
version other than 0.15.2 with an explicit error, which also surfaces
in ghostel-module-compile's compilation buffer and the auto-install
build log.  State the exact version requirement in the README.
---
 README.org      | 6 +++++-
 build.zig       | 8 ++++++++
 build.zig.zon   | 1 +
 lisp/ghostel.el | 8 ++++----
 4 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/README.org b/README.org
index de3ae370..f204e900 100644
--- a/README.org
+++ b/README.org
@@ -155,7 +155,8 @@ binaries are available for:
 - =aarch64-windows=
 
 If you prefer to build from source or need a different platform, you will also
-need [[https://ziglang.org/][Zig]] 0.15.2 - see [[#building-from-source][Building from source]].
+need *exactly* [[https://ziglang.org/][Zig]] 0.15.2 - older or newer Zig versions will not build.  See
+[[#building-from-source][Building from source]].
 
 * Installation
 :properties:
@@ -264,6 +265,9 @@ Building is only needed if you do not want the pre-built binaries.  Ghostel
 vendors a generated =vendor/emacs-module.h=, so normal builds do not require
 local Emacs headers.
 
+Building requires *exactly* [[https://ziglang.org/][Zig]] 0.15.2 - older or newer Zig versions will not build.
+Check your installed version with =zig version=.
+
 #+begin_src sh
 git clone https://github.com/dakra/ghostel.git
 cd ghostel
diff --git a/build.zig b/build.zig
index 9f1379f3..c7ed88f6 100644
--- a/build.zig
+++ b/build.zig
@@ -1,6 +1,14 @@
 const std = @import("std");
+const builtin = @import("builtin");
 const module_version = @import("src/version.zig").version;
 
+// Keep in sync with build.zig.zon (minimum_zig_version) and the CI workflows.
+const required_zig = std.SemanticVersion{ .major = 0, .minor = 15, .patch = 2 };
+comptime {
+    if (builtin.zig_version.order(required_zig) != .eq)
+        @compileError("ghostel requires exactly Zig 0.15.2, found " ++ builtin.zig_version_string);
+}
+
 const vendored_emacs_module_dir = "vendor";
 
 pub fn build(b: *std.Build) void {
diff --git a/build.zig.zon b/build.zig.zon
index ba8fa251..9c213642 100644
--- a/build.zig.zon
+++ b/build.zig.zon
@@ -1,6 +1,7 @@
 .{
     .name = .ghostel,
     .version = "0.44.0",
+    .minimum_zig_version = "0.15.2",
     .paths = .{""},
     .fingerprint = 0x5a44bdd1198a0f4b,
     .dependencies = .{
diff --git a/lisp/ghostel.el b/lisp/ghostel.el
index ec2e3644..16d1be0d 100644
--- a/lisp/ghostel.el
+++ b/lisp/ghostel.el
@@ -73,10 +73,10 @@
 ;;
 ;; Native module:
 ;;
-;;   A pre-built binary is downloaded automatically on first use.  To
-;;   build from source instead (requires Zig 0.15.2+), run zig build --prefix .
-;;   from the project root, or M-x ghostel-module-compile.  M-x
-;;   ghostel-download-module re-fetches the pre-built binary.
+;;   A pre-built binary is downloaded automatically on first use.
+;;   To build from source instead (requires exactly Zig 0.15.2), run
+;;   zig build --prefix . from the project root, or M-x ghostel-module-compile.
+;;   M-x ghostel-download-module re-fetches the pre-built binary.
 ;;
 ;; See also: evil-ghostel.el (evil-mode integration), ghostel-compile.el
 ;; (TTY-backed M-x compile replacement), ghostel-eshell.el (eshell