https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111300
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Possibly relevant, compiling anything including <stacktrace> with -Wsystem-headers -Wabi gives these warnings: /home/jwakely/gcc/13/include/c++/13.2.1/stacktrace: At global scope: /home/jwakely/gcc/13/include/c++/13.2.1/stacktrace:201:24: warning: the mangled name of 'constexpr std::stacktrace_entry::_M_get_info(std::string*, std::string*, int*) const::<lambda(void*, std::stacktrace_entry::uintptr_t, const char*, std::stacktrace_entry::uintptr_t, std::stacktrace_entry::uintptr_t)>::operator void (*)(void*, std::stacktrace_entry::uintptr_t, const char*, std::stacktrace_entry::uintptr_t, std::stacktrace_entry::uintptr_t)() const' changed between '-fabi-version=10' ('_ZZNKSt16stacktrace_entry11_M_get_infoEPNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEES6_PiENKUlPvmPKcmmE0_cvPFvS8_mSA_mmEEv') and '-fabi-version=18' ('_ZZNKSt16stacktrace_entry11_M_get_infoEPNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEES6_PiENKUlPvmPKcmmE_cvPFvS8_mSA_mmEEv') [-Wabi] 201 | auto __cb2 = [](void* __data, uintptr_t, const char* __symname, | ^ /home/jwakely/gcc/13/include/c++/13.2.1/stacktrace:201:24: warning: the mangled name of 'static constexpr void std::stacktrace_entry::_M_get_info(std::string*, std::string*, int*) const::<lambda(void*, std::stacktrace_entry::uintptr_t, const char*, std::stacktrace_entry::uintptr_t, std::stacktrace_entry::uintptr_t)>::_FUN(void*, std::stacktrace_entry::uintptr_t, const char*, std::stacktrace_entry::uintptr_t, std::stacktrace_entry::uintptr_t)' changed between '-fabi-version=10' ('_ZZNKSt16stacktrace_entry11_M_get_infoEPNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEES6_PiENUlPvmPKcmmE0_4_FUNES8_mSA_mm') and '-fabi-version=18' ('_ZZNKSt16stacktrace_entry11_M_get_infoEPNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEES6_PiENUlPvmPKcmmE_4_FUNES8_mSA_mm') [-Wabi] /home/jwakely/gcc/13/include/c++/13.2.1/stacktrace:201:24: warning: the mangled name of 'std::stacktrace_entry::_M_get_info(std::string*, std::string*, int*) const::<lambda(void*, std::stacktrace_entry::uintptr_t, const char*, std::stacktrace_entry::uintptr_t, std::stacktrace_entry::uintptr_t)>' changed between '-fabi-version=10' ('_ZZNKSt16stacktrace_entry11_M_get_infoEPNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEES6_PiENKUlPvmPKcmmE0_clES8_mSA_mm') and '-fabi-version=18' ('_ZZNKSt16stacktrace_entry11_M_get_infoEPNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEES6_PiENKUlPvmPKcmmE_clES8_mSA_mm') [-Wabi] e.g. g++ -x c++ /dev/null -include stacktrace -Wsystem-headers -std=c++23 -Wabi=10 (either using GCC 13 built with --enable-libstdcxx-backtrace or using GCC trunk before r14-3812-gb96b554592c5cb which moved the lambda out of the header into libstdc++exp.a) Those -Wabi warnings might be related to the "previous mangle" errors in the modules test.