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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Python fails to build on WASM: _testcapi/vectorcall_limited.c is built with Py_BUILD_CORE_BUILTIN","articleBody":"My PR #109690 broke WASM buildbots.\r\n\r\nExample with wasm32-emscripten node (dynamic linking) 3.x: https://buildbot.python.org/all/#/builders/1056/builds/3142\r\n\r\n```\r\n/opt/emsdk/upstream/emscripten/emcc  -DNDEBUG -g -O3 (...) -DPy_BUILD_CORE_BUILTIN -c ../../Modules/_testcapi/vectorcall_limited.c -o Modules/_testcapi/vectorcall_limited.o\r\n\r\nIn file included from ../../Modules/_testcapi/vectorcall_limited.c:2:\r\nIn file included from ../../Modules/_testcapi/parts.h:7:\r\nIn file included from ../../Include/Python.h:44:\r\n../../Include/pyport.h:52:4: error: \"Py_LIMITED_API is not compatible with Py_BUILD_CORE\"\r\n#  error \"Py_LIMITED_API is not compatible with Py_BUILD_CORE\"\r\n   ^\r\n1 error generated.\r\n```\r\n\r\nI'm not sure how ``-DPy_BUILD_CORE_BUILTIN`` landed in the command building ``Modules/_testcapi/vectorcall_limited.c``.\r\n\r\nI don't think that it's correct that ``vectorcall_limited.c`` which tests the limited C API on purpose it built with ``Py_BUILD_CORE``.\r\n\r\nOn my Linux machine, Makefile contains:\r\n\r\n```\r\nModules/_testcapi/vectorcall_limited.o: $(srcdir)/Modules/_testcapi/vectorcall_limited.c $(MODULE__TESTCAPI_DEPS) $(MODULE_DEPS_SHARED) $(PYTHON_HEADERS); $(CC) $(MODULE__TESTCAPI_CFLAGS) $(PY_STDMODULE_CFLAGS) $(CCSHARED) -c $(srcdir)/Modules/_testcapi/vectorcall_limited.c -o Modules/_testcapi/vectorcall_limited.o\r\n```\r\n\r\nSo it gets two groups of compiler flags:\r\n\r\n* ``MODULE__TESTCAPI_CFLAGS``: not defined (empty)\r\n* ``PY_STDMODULE_CFLAGS``: ``-fno-strict-overflow -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -g -Og -Wall -O0   -std=c11 -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal  -I. -I./Include``\r\n\r\nI don't see ``-DPy_BUILD_CORE_BUILTIN`` here.\r\n\r\nI can reproduce the issue locally with this custom ``Modules/Setup.local``:\r\n\r\n```\r\n*static*\r\n_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/vectorcall_limited.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/pyos.c _testcapi/immortal.c _testcapi/heaptype_relative.c _testcapi/gc.c\r\n```\r\n\r\nmake fails with:\r\n\r\n```\r\nIn file included from ./Include/Python.h:44,\r\n                 from ./Modules/_testcapi/parts.h:7,\r\n                 from ./Modules/_testcapi/vectorcall_limited.c:2:\r\n./Include/pyport.h:52:4: error: #error \"Py_LIMITED_API is not compatible with Py_BUILD_CORE\"\r\n   52 | #  error \"Py_LIMITED_API is not compatible with Py_BUILD_CORE\"\r\n      |    ^~~~~\r\nmake: *** [Makefile:2982: Modules/_testcapi/vectorcall_limited.o] Error 1\r\nmake: *** Waiting for unfinished jobs....\r\nIn file included from ./Include/Python.h:44,\r\n                 from ./Modules/_testcapi/parts.h:7,\r\n                 from ./Modules/_testcapi/heaptype_relative.c:2:\r\n./Include/pyport.h:52:4: error: #error \"Py_LIMITED_API is not compatible with Py_BUILD_CORE\"\r\n   52 | #  error \"Py_LIMITED_API is not compatible with Py_BUILD_CORE\"\r\n      |    ^~~~~\r\nmake: *** [Makefile:3001: Modules/_testcapi/heaptype_relative.o] Error 1\r\n```\r\n\r\n``Modules/makesetup`` uses ``$(PY_STDMODULE_CFLAGS)`` if ``$doconfig`` is no, but uses ``$(PY_BUILTIN_MODULE_CFLAGS)`` otherwise. In the second case, $(PY_BUILTIN_MODULE_CFLAGS) adds ``-DPy_BUILD_CORE_BUILTIN`` to compiler command used to build ``_testcapi`` C files.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-109727\n* gh-109842\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/vstinner","@type":"Person","name":"vstinner"},"datePublished":"2023-09-22T12:22:03.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/109723/cpython/issues/109723"}