https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105128
--- Comment #4 from CVS 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:2a82301d409d3aa0e0b3b884e4c6daeaa0486d6b commit r12-7968-g2a82301d409d3aa0e0b3b884e4c6daeaa0486d6b Author: Jakub Jelinek <ja...@redhat.com> Date: Sat Apr 2 12:49:38 2022 +0200 libstdc++: Tweak source_location for clang trunk [PR105128] Apparently clang trunk implemented __builtin_source_location(), but the using __builtin_ret_type = decltype(__builtin_source_location()); which has been added for it isn't enough, they also need the std::source_location::__impl class to be defined (but incomplete seems to be good enough) before the builtin is used. The following has been tested on godbolt with clang trunk (old version fails with error: 'std::source_location::__impl' was not found; it must be defined before '__builtin_source_location' is called and some follow-up errors), getting back to just void * instead of __builtin_ret_type and commenting out using doesn't work either and just struct __impl; before using __builtin_ret_type doesn't work too. 2022-04-02 Jakub Jelinek <ja...@redhat.com> PR libstdc++/105128 * include/std/source_location (std::source_location::__impl): Move definition before using __builtin_ret_type.