Python 2.7.18 — Bazel Module

Builds python27.dll from source using MSVC via the local file registry at ext_libraries/modules/python/.

Registry layout

ext_libraries/modules/python/
  metadata.json
  2.7.18/
    MODULE.bazel
    source.json          ← URL + overlay hashes
    overlay/
      MODULE.bazel
      BUILD.bazel        ← cc_binary + filegroup + cc_library
      PC/config.c        ← minimal built-in module table (replaces stock PC/config.c)
      PC/pyconfig.h      ← removes #pragma comment(lib,"python27.lib") auto-link

Targets

Target	Output
`@python//:python27`	`python27.dll` (linkshared)
`@python//:python27_implib`	`python27.if.lib` (interface_library filegroup)
`@python//:python_headers`	`Include/*.h` + `PC/pyconfig.h`

Key build decisions

`_socket` is linked in, not built as `_socket.pyd`

Upstream CPython builds a set of extension modules as separate .pyd DLLs (PCbuild/_socket.vcproj, select, unicodedata, _ssl, _ctypes, …). This port has no .pyd extension-module targets at all — python27.dll contains only what PC/config.c lists in _PyImport_Inittab.

socketmodule.c is the one exception, compiled into python27.dll and listed in the overlay's PC/config.c as {"_socket", init_socket}. It is not optional: main/pyuno/source/module/uno.py does import socket at module scope (“since on Windows sal3.dll no longer calls WSAStartup”), so without _socket every import uno raises ImportError: No module named _socket. That kills import pythonloader, so pyuno_loader.cxx's CreateInstance() throws before activate() is ever reached and the whole Python UNO loader is dead — visible as an empty tree and greyed buttons in Tools ▸ Macros ▸ Organize Macros ▸ Python, with the exception swallowed by ProviderCache. ws2_32.lib was already in linkopts.

Expect warning C4005: 'INVALID_SOCKET' : macro redefinition — socketmodule.c defines it before including the SDK's winsock2.h. Harmless, same value.

Still missing: every other extension module. A Python macro that imports select, unicodedata, _ssl, _ctypes, pyexpat, bz2 … will fail the same way. Add them the same way (source into _MODULE_SRCS + entry in PC/config.c) as they are needed, or build real .pyd targets — //build/rules:copy_file.bzl exists for the .dll → .pyd rename, see main/pyuno/readme.md.

No DEF file

Python 2.7.18's tarball does not include PC/python27.def. Exports are produced via __declspec(dllexport) through the Py_BUILD_CORE → PyAPI_FUNC macro chain. No win_def_file is needed.

PC/pyconfig.h — no ./configure needed

The Windows pre-generated PC/pyconfig.h is used directly. No autoconf step.

Defines

Py_BUILD_CORE — enables __declspec(dllexport) on all public API
NTDDI_VERSION=0x06010000 — pre-empts pyconfig.h‘s XP-era #ifndef which conflicts with the toolchain’s /D_WIN32_WINNT=0x0601 (Vista)
MS_WINDOWS, WITH_THREAD, NT_THREADS — omitted; PC/pyconfig.h already defines them (adding them again causes C4005 redefinition warnings)
snprintf=_snprintf — omitted; Python/pyport.h handles this for MSVC

include paths

Include/ — public Python headers (Python.h etc.)
PC/ — pyconfig.h (Windows pre-generated)
Python/ — internal headers (importdl.h, used by PC/import_nt.c)

Excluded source files

Python/ (Unix-only or conflicts):

File	Reason
`dynload_aix/atheos/beos/dl/hpux/os2/shlib/stub.c`	OS-specific dynloaders
`dynload_next.c`	macOS/NeXTStep — requires `mach-o/dyld.h`
`mactoolboxglue.c`	macOS — requires `Carbon/Carbon.h`
`getcwd.c`	POSIX fallback; Windows uses `_getcwd` from CRT
`dup2.c`, `strdup.c`	POSIX shims not needed on Windows
`pyfpe.c`	SIGFPE handling (Unix-only)
`sigcheck.c`	Stub superseded by `Modules/signalmodule.c`
`intrcheck.c`	Stub superseded by `Modules/signalmodule.c`
`frozenmain.c`	Frozen-exe launcher — unresolved `PyWinFreeze_*`

Parser/ (pgen build-tool files not part of the runtime DLL):

File	Reason
`pgenmain.c`	pgen `main()` — duplicates `pythonrun`/`errors` symbols
`tokenizer_pgen.c`	pgen tokenizer — duplicates `tokenizer.c` symbols
`pgen.c`	Parser generator — build tool only
`printgrammar.c`	pgen utility — build tool only
`intrcheck.c`	Stub superseded by `Modules/signalmodule.c`

Note: Parser/intrcheck.c is distinct from Python/intrcheck.c — both exist in the source tree. Both must be excluded; only the Parser/ one was causing the linker conflict (it is picked up by glob(["Parser/*.c"])).

getopt.c — kept

Python/getopt.c is Python's own command-line option parser providing _PyOS_GetOpt, _PyOS_optind, _PyOS_optarg etc. required by Modules/main.c. It is NOT a POSIX shim and must NOT be excluded.

Overlay PC/config.c

The stock PC/config.c references modules not compiled into this minimal DLL (CJK codecs, zlib, mmap, audioop, imageop, lsprof, hotshot). An overlay PC/config.c is provided that lists only the modules actually compiled in.

Overlay cache update procedure

After any change to an overlay file:

Recompute SHA-256: cat overlay/FILE | openssl dgst -sha256 -binary | base64
Update source.json with "sha256-<base64>" for the changed file
Run bazel mod deps --lockfile_mode=refresh
Run bazel build @python//:python27

If the analysis cache persists stale (observed with glob changes to external modules), run bazel shutdown before bazel mod deps --lockfile_mode=refresh.