https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117650
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Mathias Stearn from comment #0) > https://godbolt.org/z/svjPzrf5z Shows the impact on codegen by making > __GLIBCXX_NORETURN imply cold in addition to noreturn. This seemed like the > easiest way to demonstrate this. It also might be worth considering since > noreturn functions tend to be cold ones. We have noreturn imply cold in our > codebase, FWIW. These are the other uses of _GLIBCXX_NORETURN: include/c_global/cstdlib: extern "C" void abort(void) _GLIBCXX_NOTHROW _GLIBCXX_NORETURN; include/c_global/cstdlib: extern "C" void exit(int) _GLIBCXX_NOTHROW _GLIBCXX_NORETURN; include/c_global/cstdlib: extern "C" void quick_exit(int) _GLIBCXX_NOTHROW _GLIBCXX_NORETURN; include/c_global/cstdlib: extern "C" void _Exit(int) _GLIBCXX_NOTHROW _GLIBCXX_NORETURN; include/c_global/cstdlib: extern "C" void (_Exit)(int) _GLIBCXX_NOTHROW _GLIBCXX_NORETURN; include/c_std/cstdlib: extern "C" void abort(void) throw () _GLIBCXX_NORETURN; include/c_std/cstdlib: extern "C" void exit(int) throw () _GLIBCXX_NORETURN; include/c_std/cstdlib: extern "C" void quick_exit(int) throw() _GLIBCXX_NORETURN; include/c_std/cstdlib: extern "C" void (_Exit)(int) throw () _GLIBCXX_NORETURN; include/debug/formatter.h: _GLIBCXX_NORETURN void The last one is __gnu_debug::_Error_formatter::_M_error, which should definitely be cold. I'm less sure about the libc functions. Glibc doesn't mark them as cold. I think for now I'll just explicitly add __attribute__((__cold__)) to __glibcxx_assert_fail and _Error_formatter::_M_error. We also have a few uses of __noreturn__ directly, without the macro (both as __attribute__((__noreturn__)) and oddly, [[__noreturn__]] which could just be [[noreturn]] because that was in C++11.
