build: keep _build_shared.py as identical copies

.pre-commit-config.yaml

@@ -81,6 +81,16 @@ repos:
         language: python
         files: '^cuda_core/tests/.*\.py$'
 
+      - id: check-build-shared-sync
+        name: Check _build_shared.py copies are identical
+        language: system
+        pass_filenames: false
+        files: '^(cuda_bindings|cuda_core)/_build_shared\.py$'
+        entry: bash -c
+        args:
+          - 'git diff --no-index --exit-code -- cuda_bindings/_build_shared.py cuda_core/_build_shared.py || { echo "ERROR: cuda_bindings/_build_shared.py and cuda_core/_build_shared.py must be byte-identical. Copy one onto the other and commit both." >&2; exit 1; }'
+          - "_" # fake script name, because bash considers $0 (the first argument) to be the script name
+
       - id: no-markdown-in-docs-source
         name: Prevent markdown files in docs/source directories
         entry: bash -c

CONTRIBUTING.md

@@ -44,10 +44,11 @@ Thank you for your interest in contributing to CUDA Python! Based on the type of
 
 ## Cloning the repository
 
-> **Windows contributors (not WSL):** configure Git for symlinks *before*
-> cloning, or the shared PEP 517 build-hook file lands as a text stub instead
-> of a working symlink. See [Enabling git symlinks](#enabling-git-symlinks)
-> under Development on Windows.
+> **Windows contributors (not WSL):** source builds and tests work with
+> `core.symlinks=false`. Git symlink support is optional and only affects the
+> remaining documentation and metadata links (`CLAUDE.md`,
+> `cuda_python/README.md`, and `.git_archival.txt`). See
+> [Enabling git symlinks](#enabling-git-symlinks) if you want those links materialized.
 
 Every package in this repository derives its version from git tags using
 [`setuptools-scm`](https://setuptools-scm.readthedocs.io/), so **how you clone
@@ -137,18 +138,18 @@ genuinely cannot provide tags; it is not a substitute for a correct clone.
 
 ## Development on Windows
 
-This section collects the Windows-specific setup a contributor needs when
-working outside of WSL. WSL contributors can follow the Linux flow in the rest
-of this document.
+This section collects Windows-specific guidance for contributors working
+outside of WSL. WSL contributors can follow the Linux flow in the rest of this
+document.
 
 ### Enabling git symlinks
 
-The `cuda_core` PEP 517 backend shares source-of-truth helper files with
-`cuda_bindings` via symbolic links. Git materializes symlinks by default on
-Linux and macOS, but on Windows it needs to be configured before cloning,
-otherwise the "symlinks" land in your working tree as plain text files that
-contain the target path — enough to look right in `git status`, but not enough
-to actually build.
+The repository still contains documentation and metadata symlinks, including
+`CLAUDE.md`, `cuda_python/README.md`, and the per-package `.git_archival.txt`
+files. With `core.symlinks=false`, Git checks them out as plain text files
+containing the target path. This does not affect source builds or tests.
+
+If you want these links materialized as symlinks:
 
 1. **[Activate Developer Mode](https://learn.microsoft.com/en-us/windows/apps/get-started/enable-your-device-for-development#activate-developer-mode)**
    so Git can create symlinks without Administrator privileges.
@@ -162,22 +163,19 @@ to actually build.
 
 Then clone as usual (see [Cloning the repository](#cloning-the-repository)).
 
-If you already cloned without these settings, note that `git clone` probes
-symlink support at clone time and writes `core.symlinks=false` into the
-repo-local config when the probe fails. Repo-local config overrides
-`--global`, so you must clear it *inside the existing clone* — the global
-setting alone won't take effect:
+If you already cloned with `core.symlinks=false`, the repository-local
+setting overrides the global setting. Enable it locally, then rematerialize
+all tracked symlinks. For example:
 
 ```console
-$ git config core.symlinks true          # no --global — clears the repo-local override
-$ git rm --cached cuda_core/_build_shared.py
-$ git checkout HEAD -- cuda_core/_build_shared.py
+$ git config core.symlinks true
+$ git rm --cached cuda_python/README.md
+$ git checkout HEAD -- cuda_python/README.md
 ```
 
-In practice, deleting the checkout and re-cloning after the two steps at
-the top of this section (Developer Mode + `git config --global core.symlinks
-true`) is usually simpler and less error-prone than repairing an existing
-clone in place.
+Repeat the last two commands for every other tracked symlink. Re-cloning after
+enabling Developer Mode and setting the global option is simpler if you want
+all links restored.
 
 ### Pre-commit lychee workaround
 

cuda_bindings/AGENTS.md

@@ -21,8 +21,9 @@ subpackage in the `cuda-python` monorepo.
 - **Build backend**: `build_hooks.py` drives extension configuration and
   Cythonization. Logic shared with `cuda_core` (toolchain selection, the
   compiler flag set, the Cython cache helpers and the rebuild stamps) lives
-  in `_build_shared.py`; `cuda_core/_build_shared.py` is a symlink to this
-  file, so an edit here changes both packages.
+  in `_build_shared.py`. `cuda_bindings/_build_shared.py` is canonical;
+  `cuda_core/_build_shared.py` must be either a symlink to it or a byte-for-byte
+  identical copy.
 
 ## Generated-source workflow
 

cuda_bindings/MANIFEST.in

@@ -6,5 +6,5 @@ recursive-include cuda/ *.pyx *.pxd *.pxi *.pyx.in *.pxd.in *.pxi.in *.h
 # to the payload, causing file copying to the build environment failed
 exclude cuda/bindings cuda?bindings
 exclude cuda/bindings/_bindings cuda?bindings?_bindings
-# canonical shared PEP 517 helper (cuda_core/_build_shared.py symlinks to the cuda_bindings copy)
+# package-local shared PEP 517 helper
 include _build_shared.py

cuda_bindings/_build_shared.py

@@ -3,10 +3,10 @@
 
 """Build helpers shared by the cuda-bindings and cuda-core PEP 517 backends.
 
-This is the single source of truth. ``cuda_core/_build_shared.py`` is a symlink
-to this file. Python does not dereference symlinks in ``__file__``, so any
-``Path(__file__)``-relative location in here resolves under whichever package
-loads it.
+``cuda_bindings/_build_shared.py`` is canonical. ``cuda_core/_build_shared.py``
+is either a symlink to it or a byte-for-byte identical copy. Both backends load
+the helper through their package-local path, keeping ``Path(__file__)``-relative
+state package-local.
 
 PEP 517 build isolation gives each backend its own ``build_hooks.py`` but not a
 shared import path. Both packages declare ``backend-path = ["."]``, which puts
@@ -385,9 +385,8 @@ def _stable_cython_alias(target: Path, alias: Path):
     unstable across runs. This context manager creates a fixed, worktree-
     relative symlink so Cython sees a stable lexical path.
 
-    The symlink is created in the *package directory* (the directory containing
-    this file, which is the package's own copy through the symlink), not in
-    the cwd, to keep aliases package-local and avoid cross-package races.
+    The symlink is created in the package directory containing this file, not
+    in the cwd, to keep aliases package-local and avoid cross-package races.
 
     alias must not already exist as a real file or directory; if it is a
     symlink (including a dangling one) it is atomically replaced.

cuda_bindings/docs/source/install.rst

@@ -126,7 +126,7 @@ Requirements
 
 [^2]: The CUDA Runtime static library (``libcudart_static.a`` on Linux, ``cudart_static.lib`` on Windows) is part of the CUDA Toolkit. If using conda packages, it is contained in the ``cuda-cudart-static`` package.
 
-[^3]: The version is derived from git tags via ``setuptools-scm``, so the clone must include tags reaching back to at least the latest ``v*`` tag. Clone with ``git clone https://github.com/NVIDIA/cuda-python.git``; do not use ``--depth`` or ``--no-tags``, since a shallow clone builds without error but produces a bogus version such as ``0.1.dev1+g0d22cb444``. See `Cloning the repository <https://github.com/NVIDIA/cuda-python/blob/main/CONTRIBUTING.md>`_ for details and recovery steps. Windows contributors building outside of WSL should also see `Development on Windows <https://github.com/NVIDIA/cuda-python/blob/main/CONTRIBUTING.md#development-on-windows>`_ for the git-symlink configuration that must be set *before* cloning.
+[^3]: The version is derived from git tags via ``setuptools-scm``, so the clone must include tags reaching back to at least the latest ``v*`` tag. Clone with ``git clone https://github.com/NVIDIA/cuda-python.git``; do not use ``--depth`` or ``--no-tags``, since a shallow clone builds without error but produces a bogus version such as ``0.1.dev1+g0d22cb444``. See `Cloning the repository <https://github.com/NVIDIA/cuda-python/blob/main/CONTRIBUTING.md>`_ for details and recovery steps.
 
 Source builds require that the provided CUDA headers are of the same major.minor version as the ``cuda.bindings`` you're trying to build. Despite this requirement, note that the minor version compatibility is still maintained. The build checks the header before it compiles anything. A mismatch stops the build with a message that names the ``cuda.h`` it found and the version this source tree needs. Use the ``CUDA_PATH`` (or ``CUDA_HOME``) environment variable to specify the location of your headers. If both are set, ``CUDA_PATH`` takes precedence. For example, if your headers are located in ``/usr/local/cuda/include``, then you should set ``CUDA_PATH`` with:
 

cuda_core/AGENTS.md

@@ -25,8 +25,9 @@ This file describes `cuda_core`, the high-level Pythonic CUDA subpackage in the
 - **Build backend**: `build_hooks.py` handles Cython extension setup and build
   dependency wiring. Logic shared with `cuda_bindings` (toolchain selection,
   the compiler flag set, the Cython cache helpers and the rebuild stamps)
-  lives in `_build_shared.py`, a symlink to `cuda_bindings/_build_shared.py`; an edit through either path changes both
-  packages.
+  lives in `_build_shared.py`. `cuda_bindings/_build_shared.py` is canonical;
+  `cuda_core/_build_shared.py` must be either a symlink to it or a byte-for-byte
+  identical copy.
 
 ## Build and version coupling
 

cuda_core/MANIFEST.in

@@ -7,5 +7,5 @@ recursive-include cuda/core/_cpp *.cpp *.h *.hpp
 recursive-include cuda/core/_include *.h *.hpp
 include cuda/core/py.typed
 include NOTICE
-# canonical shared PEP 517 helper (cuda_core/_build_shared.py symlinks to the cuda_bindings copy)
+# package-local shared PEP 517 helper
 include _build_shared.py