https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69560
--- Comment #25 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:ac8c61b62e71ffdcaebfd4cfc03f58fe542855dd commit r15-1713-gac8c61b62e71ffdcaebfd4cfc03f58fe542855dd Author: Jonathan Wakely <jwak...@redhat.com> Date: Wed Jun 26 12:40:51 2024 +0100 libstdc++: Simplify <ext/aligned_buffer.h> class templates As noted in a comment, the __gnu_cxx::__aligned_membuf class template can be simplified, because alignof(T) and alignas(T) use the correct alignment for a data member. That's true since GCC 8 and Clang 8. The EDG front end (as used by Intel icc, aka "Intel C++ Compiler Classic") does not implement the PR c++/69560 change, so keep using the old implementation when __EDG__ is defined, to avoid an ABI change for icc. For __gnu_cxx::__aligned_buffer<T> all supported compilers agree on the value of __alignof__(T), but we can still simplify it by removing the dependency on std::aligned_storage<sizeof(T), __alignof__(T)>. Add a test that checks that the aligned buffer types have the expected alignment, so that we can tell if changes like this affect their ABI properties. libstdc++-v3/ChangeLog: * include/ext/aligned_buffer.h (__aligned_membuf): Use alignas(T) directly instead of defining a struct and using 9its alignment. (__aligned_buffer): Remove use of std::aligned_storage. * testsuite/abi/aligned_buffers.cc: New test.
