From 90758a14d0a74190e0eb4f29ae811a17fdd4a7a5 Mon Sep 17 00:00:00 2001
From: Jakob Nybo Andersen <jnandersen@proton.me>
Date: Thu, 12 Feb 2026 08:07:08 +0100
Subject: [PATCH] Bugfix: Negative bytes to readbytes!

---
 .github/workflows/tagbot.yml | 25 ++++++++++++++++++++
 AGENTS.md                    | 45 ++++++++++++++++++++++++++++++++++++
 CLAUDE.md                    | 42 +--------------------------------
 src/io.jl                    |  1 +
 test/runtests.jl             |  3 +++
 5 files changed, 75 insertions(+), 41 deletions(-)
 create mode 100644 .github/workflows/tagbot.yml
 create mode 100644 AGENTS.md

diff --git a/.github/workflows/tagbot.yml b/.github/workflows/tagbot.yml
new file mode 100644
index 0000000..ae4d242
--- /dev/null
+++ b/.github/workflows/tagbot.yml
@@ -0,0 +1,25 @@
+name: TagBot
+on:
+  issue_comment:
+    types:
+      - created
+  workflow_dispatch:
+    inputs:
+      lookback:
+        description: "[DEPRECATED] No longer has any effect"
+        default: "3"
+jobs:
+  TagBot:
+    if: github.event_name == 'workflow_dispatch' || github.actor == 'JuliaTagBot'
+    runs-on: ubuntu-slim
+    steps:
+      - uses: JuliaRegistries/TagBot@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          # For commits that modify workflow files: SSH key enables tagging, but
+          # releases require manual creation. For full automation of such commits,
+          # use a PAT with `workflow` scope instead of GITHUB_TOKEN.
+          # See: https://github.com/JuliaRegistries/TagBot#commits-that-modify-workflow-files
+          ssh: ${{ secrets.DOCUMENTER_KEY }}
+          # ssh: ${{ secrets.NAME_OF_MY_SSH_PRIVATE_KEY_SECRET }}
+          # changelog_format: github  # 'custom' (default), 'github', or 'conventional'
diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..4c8c9f8
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,45 @@
+# AGENTS.md
+
+This file provides guidance to LLMs when working with code in this repository.
+
+## Project Overview
+
+MemoryViews.jl provides `MemoryView`, a low-level view into `Memory{T}` for Julia ≥ 1.11. It's a `DenseVector{T}` subtype representing a `MemoryRef{T}` + length, with static mutability tracking via type parameter (`Mutable`/`Immutable`). The package also defines the `MemoryKind` trait for dispatch on memory-backed types.
+
+## Commands
+
+```bash
+# Run tests
+JULIA_TEST_FAILFAST=true julia --startup=no --project -e 'using Pkg; Pkg.test()'
+
+# Format code
+runic -i .
+```
+
+When running in test mode, Julia has boundscheck always enabled. When running normally,
+out-of-bounds access in functions marked `@inbounds` is undefined behaviour.
+Set `--check-bounds=yes` to force boundschecking when running experiments.
+
+## Architecture
+
+**Core types** (defined in `src/MemoryViews.jl`):
+- `MemoryView{T, M}` where `M ∈ {Mutable, Immutable}` — the main type
+- `MemoryKind` trait: `IsMemory{T}` / `NotMemory` for dispatch
+
+**Source files**:
+- `construction.jl` — constructors from Array, Memory, String, SubArray, CodeUnits
+- `basic.jl` — indexing, slicing (returns views, not copies), copying, find operations with memchr/memrchr C calls, comparison via memcmp
+- `experimental.jl` — `split_first`, `split_last`, `split_at`, `split_unaligned`
+- `delimited.jl` — `split_each` delimiter iterator
+- `base_arrays.jl` — Vector/Memory conversion, append
+- `io.jl` — `readbytes!`
+
+**Extensions** (`ext/`): StringViews, FixedSizeArrays, LibDeflate integration.
+
+## Key Patterns
+
+- Slicing creates views into the same memory (no allocation)
+- Performance-critical paths use `@ccall` to libc (`memset`, `memcmp`, `memchr`, `memrchr`) with `GC.@preserve`
+- Version-conditional code for Julia 1.12+ vs 1.13+ (e.g., `Base.memoryindex` for `parentindices`)
+- Trait-based dispatch pattern: define `foo(x)` → `foo(MemoryKind(typeof(x)), x)` → specialized on `IsMemory`/`NotMemory`
+- `@boundscheck`/`@inbounds` used throughout for safe-by-default with opt-in elision
diff --git a/CLAUDE.md b/CLAUDE.md
index cc6c085..43c994c 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -1,41 +1 @@
-# CLAUDE.md
-
-This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
-
-## Project Overview
-
-MemoryViews.jl provides `MemoryView`, a low-level view into `Memory{T}` for Julia ≥ 1.11. It's a `DenseVector{T}` subtype representing a `MemoryRef{T}` + length, with static mutability tracking via type parameter (`Mutable`/`Immutable`). The package also defines the `MemoryKind` trait for dispatch on memory-backed types.
-
-## Commands
-
-```bash
-# Run tests
-JULIA_TEST_FAILFAST=true julia --project -e 'using Pkg; Pkg.test()'
-
-# Format code
-runic -i .
-```
-
-## Architecture
-
-**Core types** (defined in `src/MemoryViews.jl`):
-- `MemoryView{T, M}` where `M ∈ {Mutable, Immutable}` — the main type
-- `MemoryKind` trait: `IsMemory{T}` / `NotMemory` for dispatch
-
-**Source files**:
-- `construction.jl` — constructors from Array, Memory, String, SubArray, CodeUnits
-- `basic.jl` — indexing, slicing (returns views, not copies), copying, find operations with memchr/memrchr C calls, comparison via memcmp
-- `experimental.jl` — `split_first`, `split_last`, `split_at`, `split_unaligned`
-- `delimited.jl` — `split_each` delimiter iterator
-- `base_arrays.jl` — Vector/Memory conversion, append
-- `io.jl` — `readbytes!`
-
-**Extensions** (`ext/`): StringViews, FixedSizeArrays, LibDeflate integration.
-
-## Key Patterns
-
-- Slicing creates views into the same memory (no allocation)
-- Performance-critical paths use `@ccall` to libc (`memset`, `memcmp`, `memchr`, `memrchr`) with `GC.@preserve`
-- Version-conditional code for Julia 1.12+ vs 1.13+ (e.g., `Base.memoryindex` for `parentindices`)
-- Trait-based dispatch pattern: define `foo(x)` → `foo(MemoryKind(typeof(x)), x)` → specialized on `IsMemory`/`NotMemory`
-- `@boundscheck`/`@inbounds` used throughout for safe-by-default with opt-in elision
+@AGENTS.md
diff --git a/src/io.jl b/src/io.jl
index 623c4cb..5386d0b 100644
--- a/src/io.jl
+++ b/src/io.jl
@@ -4,6 +4,7 @@
 # This encourages implementors of IOs to implement a method for this.
 function Base.readbytes!(io::IO, v::MutableMemoryView{UInt8}, nb::Integer = length(v))
     nb = Int(nb)::Int
+    nb < 0 && throw(ArgumentError("Cannot read negative amount of bytes"))
     # A view of all the bytes not yet read
     remaining = @inbounds v[1:min(nb, length(v))]
     while !isempty(remaining)
diff --git a/test/runtests.jl b/test/runtests.jl
index 870422f..26727eb 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -668,6 +668,9 @@ end
     v = fill(0xaa, 8)
     readbytes!(buf, MemoryView(v), 10)
     @test v == b"Hello, w"
+
+    # Negative nb is invalid
+    @test_throws ArgumentError readbytes!(IOBuffer(data), MemoryView(v), -1)
 end
 
 @testset "Base arrays" begin