[libcxx] Mark system_reserved_names.gen.py unsupported on clang-20 && msvc #161811
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… msvc Clang 20 (and early 21 versions; let's hope it can be fixed before the later versions before such versions become relevant for libcxx CI) have got an issue with its intrinsics headers, where they use unreserved names, that users are allowed to override. See llvm#161808 for the issue report. This only crops up in the MSVC build configurations, as recent versions of some MSVC/UCRT headers include `<intrin.h>`, which ends up pulling in most intrinsics headers, exposing this issue in the Clang headers. This should unblock llvm#161736 from being merged.
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@llvm/pr-subscribers-libcxx Author: Martin Storsjö (mstorsjo) ChangesClang 20 (and early 21 versions; let's hope it can be fixed before the later versions before such versions become relevant for libcxx CI) have got an issue with its intrinsics headers, where they use unreserved names, that users are allowed to override. See #161808 for the issue report. This only crops up in the MSVC build configurations, as recent versions of some MSVC/UCRT headers include This should unblock #161736 from being merged. Full diff: https://github.com/llvm/llvm-project/pull/161811.diff 1 Files Affected:
diff --git a/libcxx/test/libcxx/system_reserved_names.gen.py b/libcxx/test/libcxx/system_reserved_names.gen.py
index f8589f2beaae3..d69182d68e0de 100644
--- a/libcxx/test/libcxx/system_reserved_names.gen.py
+++ b/libcxx/test/libcxx/system_reserved_names.gen.py
@@ -10,6 +10,13 @@
# alphabetic macros. Also ensure that we don't swallow the definition of user
# provided macros (in other words, ensure that we push/pop correctly everywhere).
+# This test fails with MSVC headers, with Clang 20 (and early 21 versions);
+# the headers end up pulling in Clang intrinsics headers, which in 20.x and
+# early 21.x versions use unreserved identifiers,
+# see https://github.com/llvm/llvm-project/issues/161808.
+#
+# UNSUPPORTED: clang-20 && msvc
+
# RUN: %{python} %s %{libcxx-dir}/utils
# END.
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philnik777
approved these changes
Oct 3, 2025
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Clang 20 (and early 21 versions; let's hope it can be fixed before the later versions before such versions become relevant for libcxx CI) have got an issue with its intrinsics headers, where they use unreserved names, that users are allowed to override.
See #161808 for the issue report.
This only crops up in the MSVC build configurations, as recent versions of some MSVC/UCRT headers include
<intrin.h>, which ends up pulling in most intrinsics headers, exposing this issue in the Clang headers.This should unblock #161736 from being merged.