https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96952
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Eric Botcazou from comment #4) > What about detecting the support at configure time and defining a macro > during the compilation? Everyone has been doing this for more that 3 > decades... Sorry, but it doesn't work. How do you suggest libstdc++ should use configure-time checks to find out what features are present in the compiler including the libstdc++ headers later? I don't know what that compiler is at configure time. For example, installed libstdc++ headers might get included by the GCC release that they belong to, or by unknown releases of Clang or ICC with different feature sets and levels of standard conformance. Checking anything at configure time is useless for code in headers.
