https://github.com/python/cpython/commit/edf803345a5c57c38fca3850386530e30b397eca commit: edf803345a5c57c38fca3850386530e30b397eca branch: main author: Joshua Root <j...@macports.org> committer: ned-deily <n...@python.org> date: 2025-01-22T04:25:30-05:00 summary:
gh-128902: Fix check for fallthrough attribute support (#128903) Clang versions prior to 10 (which corresponds to Apple Clang 12) do not support the GCC extension syntax __attribute__((fallthrough)), but do evaluate __has_attribute(fallthrough) to 1 because they support the C++11 style syntax [[fallthrough]]. The only way to tell if the GCC style syntax is supported is thus to check the clang version. Ref: https://github.com/llvm/llvm-project/commit/1e0affb6e564b7361b0aadb38805f26deff4ecfc files: A Misc/NEWS.d/next/Build/2025-01-16-03-35-37.gh-issue-128902.Dt7xtV.rst M Include/pyport.h diff --git a/Include/pyport.h b/Include/pyport.h index 2b6bd4c21110e5..aabd094df54a74 100644 --- a/Include/pyport.h +++ b/Include/pyport.h @@ -625,8 +625,13 @@ extern "C" { // case 2: code; break; // } // -// __attribute__((fallthrough)) was introduced in GCC 7. -#if _Py__has_attribute(fallthrough) +// __attribute__((fallthrough)) was introduced in GCC 7 and Clang 10 / +// Apple Clang 12.0. Earlier Clang versions support only the C++11 +// style fallthrough attribute, not the GCC extension syntax used here, +// and __has_attribute(fallthrough) evaluates to 1. +#if _Py__has_attribute(fallthrough) && (!defined(__clang__) || \ + (!defined(__apple_build_version__) && __clang_major__ >= 10) || \ + (defined(__apple_build_version__) && __clang_major__ >= 12)) # define _Py_FALLTHROUGH __attribute__((fallthrough)) #else # define _Py_FALLTHROUGH do { } while (0) diff --git a/Misc/NEWS.d/next/Build/2025-01-16-03-35-37.gh-issue-128902.Dt7xtV.rst b/Misc/NEWS.d/next/Build/2025-01-16-03-35-37.gh-issue-128902.Dt7xtV.rst new file mode 100644 index 00000000000000..42ac492498e029 --- /dev/null +++ b/Misc/NEWS.d/next/Build/2025-01-16-03-35-37.gh-issue-128902.Dt7xtV.rst @@ -0,0 +1 @@ +Fix compile errors with Clang 9 and older due to lack of ``__attribute__((fallthrough))`` support. _______________________________________________ Python-checkins mailing list -- python-checkins@python.org To unsubscribe send an email to python-checkins-le...@python.org https://mail.python.org/mailman3/lists/python-checkins.python.org/ Member address: arch...@mail-archive.com
