https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121552
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:828c48f0680e209e96bcb76a232665ed047e92cc commit r16-3225-g828c48f0680e209e96bcb76a232665ed047e92cc Author: Jakub Jelinek <ja...@redhat.com> Date: Fri Aug 15 22:36:18 2025 +0200 c++: Implement C++20 P1766R1 - Mitigating minor modules maladies [PR121552] The following patch attempts to implement the C++20 P1766R1 - Mitigating minor modules maladies paper. clang++ a few years ago introduced for the diagnostics required in the paper -Wnon-c-typedef-for-linkage pedwarn and the following patch does that too. The paper was accepted as a DR, the patch enables the warning also for C++98, dunno whether it might not be better to do it only for C++11 onwards. The paper is also about differences in default arguments of functions in different TUs and in modules, I think within the same TU we diagnose it correctly (maybe I should add some testcase) and perhaps try something with modules as well. But in different TUs it is IFNDR. 2025-08-15 Jakub Jelinek <ja...@redhat.com> PR c++/121552 gcc/ * doc/invoke.texi (-Wno-non-c-typedef-for-linkage): Document. gcc/c-family/ * c.opt (Wnon-c-typedef-for-linkage): New option. * c.opt.urls: Regenerate. gcc/cp/ * decl.cc: Implement C++20 P1766R1 - Mitigating minor modules maladies. (diagnose_non_c_class_typedef_for_linkage, maybe_diagnose_non_c_class_typedef_for_linkage): New functions. (name_unnamed_type): Call maybe_diagnose_non_c_class_typedef_for_linkage. gcc/testsuite/ * g++.dg/cpp2a/typedef1.C: New test. * g++.dg/debug/dwarf2/typedef5.C: Add -Wno-non-c-typedef-for-linkage to dg-options. * g++.dg/inherit/typeinfo1.C: Add -Wno-non-c-typedef-for-linkage to dg-additional-options. * g++.dg/parse/ctor2.C: Likewise. * g++.dg/ext/anon-struct9.C: Add -Wno-non-c-typedef-for-linkage to dg-options. * g++.dg/ext/visibility/anon11.C: Add -Wno-non-c-typedef-for-linkage to dg-additional-options. * g++.dg/lto/pr69137_0.C: Add -Wno-non-c-typedef-for-linkage to dg-lto-options. * g++.dg/other/anon8.C: Add -Wno-non-c-typedef-for-linkage to dg-additional-options. * g++.dg/template/pr84973.C: Likewise. * g++.dg/template/pr84973-2.C: Likewise. * g++.dg/template/pr84973-3.C: Likewise. * g++.dg/abi/anon2.C: Likewise. * g++.dg/abi/anon3.C: Likewise. * g++.old-deja/g++.oliva/linkage1.C: Likewise.
