On 12 November 2014 13:41, Dominik Vogt wrote: > However, this does not work with a plain gcc call, i.e. gcc does > not define __STDC_VERSION__ (or __STDC__) if not told explicitly > which standard to use, e.g. with --std=c99. That's not quite accurate - you can tell gcc to explicitly use -std=c90 and it doesn't define it, or you can use current trunk with no -std option and it defines it (because trunk defaults to C11). GCC does not define __STDC_VERSION__ unless compiling C99 or later, because (I believe) that's when the macro was first defined. So it's nothing to do with an explicit -std option, it's to do with the language version being used, implicitly or explicitly. But to answer your question, any non-prehistoric version of GCC supports _Complex even in C90/GNU90 mode, unless -Werror=pedantic (the option formerly knows as -pedantic-errors) is in use. So if you want to know that GCC supports _Complex and won't give a diagnostic for its use, __STDC_VERSION__ seems like the right option.
