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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"MSVC emits warnings in non-debug builds","articleBody":"Since https://github.com/python/cpython/pull/130398, the below warning is emitted several times in case of MSVC release (or PGO) builds:\n```\nInclude\\internal\\pycore_ceval.h(209): warning C4172: returning address of local variable or temporary : here\n``` \nSo the comment in the code\nhttps://github.com/python/cpython/blob/55815a6474c59001f0230e44560341b643268e87/Include/internal/pycore_ceval.h#L202-L211\nonly works for debug builds. This is because in case of optimizing, MSVC is inlining `return_pointer_as_int` \n\nhttps://github.com/python/cpython/blob/55815a6474c59001f0230e44560341b643268e87/Include/internal/pycore_ceval.h#L196-L200\n\nand then is \"smart\" enough to realize and warn about it.\n\nSee here https://godbolt.org/z/ooK5Poxo3 (btw gcc or clang won't do that https://godbolt.org/z/459f6hj9G).\n\n[__declspec(noinline)](https://godbolt.org/z/Mh856qbnv) would help, but IMHO is an unneeded performance penalty.\n\n\n ~~I suggest to use `#pragma warning(disable:4172)` to silence the warning.~~ \n~~Since this is a [code generation warning (4700-4999)](https://learn.microsoft.com/cpp/preprocessor/warning?view=msvc-170), we have to guard the whole \n`_Py_get_machine_stack_pointer` and cannot just place it around line 209.~~\n\n@colesbury had a much better idea: use [_AddressOfReturnAddress](https://learn.microsoft.com/cpp/intrinsics/addressofreturnaddress?view=msvc-170) which even gets rid of UB: see https://godbolt.org/z/7c9Gq9jzM and https://github.com/llvm/llvm-project/blob/llvmorg-10.0.0-rc1/clang/lib/Basic/Stack.cpp#L24.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-131289\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/chris-eibl","@type":"Person","name":"chris-eibl"},"datePublished":"2025-03-15T15:11:19.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/131288/cpython/issues/131288"}