https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118244
--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> --- Libstdc++ does this for mingw-w64: // Make sure that POSIX printf/scanf functions are activated. As // libstdc++ depends on POSIX-definitions of those functions, we define // it unconditionally. #undef __USE_MINGW_ANSI_STDIO #define __USE_MINGW_ANSI_STDIO 1 So I don't think your -D__USE_MINGW_ANSI_STDIO=0 would have any effect, it would be overridden for libstdc++ code anyway.
