Fix test_venv on Windows adding support for building python launchers
#422
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This adds logic to build the following Windows-specific Python launchers: - `venvlauncher` and `venvwlauncher` (available in Python >= 3.3) - `pylauncher` and `pywlauncher` (available in Python >= 3.11) Both `launcher.c` and `launcher2.c` source files are used depending on the target. These launchers integrate Python-specific runtime behavior for virtual environments and shebang redirection on Windows. To avoid build issues on MSVC due to the `_WINDOWS` macro being defined via `CMAKE_C_FLAGS` (see CMake #19796), we introduce a helper function `add_executable_without_windows()` that: - Temporarily removes `/D_WINDOWS` from `CMAKE_C_FLAGS` - Adds `/U_WINDOWS` to ensure `_WINDOWS` is not defined - Restores the original flags after each target is added This avoids conflicts in console launchers (e.g., incorrect subsystem or entry point resolution), and resolves CVTRES and LNK1123 errors that can occur when `_WINDOWS` is incorrectly defined. Additionally, `/MANIFEST:NO` is passed to the linker to prevent duplicate resource errors due to `pylauncher.rc` already embedding a manifest.
… global flags Follow-up to the initial support for building Windows Python launchers. Instead of modifying the global `CMAKE_C_FLAGS` to remove `/D_WINDOWS` (which is unreliable due to how CMake handles cached variables) this patch uses `target_compile_options()` to explicitly undefine `_WINDOWS` at the target level. This effectively resolves the original issue while introducing the following MSVC warning: ``` cl : command line warning D9025: overriding '/D_WINDOWS' with '/U_WINDOWS' [C:\D\T\jcfr\pycbs-3.12-build\CMakeBuild\launcher\pylaunc her.vcxproj] ```
Although `venvlauncher` was introduced in Python 3.3, this change raises the minimum required version to Python 3.9 to avoid complications related to resource generation. Specifically, earlier versions require generating `pythonnt_rc.h`, which was removed in python/cpython@4efc3360c9a ("bpo-41054: Simplify resource compilation on Windows") This simplifies the build logic by eliminating the need to maintain or conditionally generate legacy resource files.
test_venv adding support for building windows python launchers test_venv on Windows adding support for building python launchers
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Summary
This pull request adds support for building the following Windows-specific Python launchers:
venvlauncherandvenvwlauncher. Introduced in Python ≥ 3.3, but only built when Python ≥ 3.9 to simplify resource handling.pylauncherandpywlauncher. Introduced and built when Python ≥ 3.11.These launchers rely on
launcher.candlauncher2.c, depending on the target. They enable Python-specific runtime behavior for virtual environments and support shebang redirection on Windows.Implementation Notes
_WINDOWSMacro HandlingTo avoid build issues related to the
_WINDOWSmacro being implicitly defined via/D_WINDOWS(e.g., fromCMAKE_C_FLAGS), we introduce a helper function:This function:
Adds the executable target using
add_executable(...)Explicitly undefines
_WINDOWSusing:Avoids modifying global variables like
CMAKE_C_FLAGS, which are unreliable and fragile during CMake generationAccepts that the following harmless MSVC warning will be emitted:
This prevents incorrect subsystem settings or entry-point mismatches that would otherwise occur if
_WINDOWSwere incorrectly defined, particularly in console-mode launchers.Manifest Handling
/MANIFEST:NOto the linker to avoid resource duplication errors, sincepylauncher.rcalready includes an embedded manifest.Conditional Launcher Build Logic
venvlauncherandvenvwlauncherare only built whenPY_VERSION ≥ 3.9.pythonnt_rc.h."bpo-41054: Simplify resource compilation on Windows (GH-21004)".
Working toward addressing: