https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103240
--- Comment #5 from frankhb1989 at gmail dot com --- There are multiple issues. 1. The out-of-line definition and the inline definition of std::type_info::before do different things. Specifically, only one name is detected against to '*' in the former, but two in the latter. It seems the latter is more correct. ("More", because it is still not quite correct, see below.) 2. As stated in https://reviews.llvm.org/D100134, mixture of different methods of comparisons breaks the ordering. I've actually encountered the problem with std::type_index as the key type when using flat_map::emplace (like https://github.com/WG21-SG14/SG14/blob/master/SG14/flat_map.h, which uses std::partition_point to find the position of insertion). The insertion suddenly fails when std::partition_point meets two std::type_info objects x and y which are unordered. It works with the workaround '-U__GXX_MERGED_TYPEINFO_NAMES -D__GXX_MERGED_TYPEINFO_NAMES=1' in the compiler command line, but it seems not enough in general without fixing the issue 2 here. (Although the same sequence of key on std::map does not fail, occasionally, due to less comparisons are made.) 3. Not sure the original change in r179236 is correct. 4. '||' in the condition of the inline definition of std::type_info::before seems an overkill. '&&' may be enough. Assuming string comparison is more expensive, this is a simple optimization. But once the issue 2 is fixed, the change would look quite different.