https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53769
--- Comment #21 from Florian Weimer <fw at gcc dot gnu.org> --- (In reply to Jakub Jelinek from comment #20) > It is not that easy. __STDC_NO_THREADS__ is a predefined macro, so it would > mean (at least on targets without stdc-predef.h, with that header one would > hope that the library describes its implementation correctly) the compiler > would need on every single compilation try to internally #if > !__has_include(<threads.h>) #define __STDC_NO_THREADS__ #endif or so. I think this would have to be configured at compiler build time. Otherwise the macro gets defined if an -I directory happens to contain a file called threads.h. I don't think alternative libcs are a thing on Darwin, and I don't expect Apple to implement support, so it's probably safe for now to define __STDC_NO_THREADS__ unconditionally on Darwin.
