Can we assume/require C99 or higher?

[mseminatore]

I am not sure what the min C compiler support level is for OpenBLAS. I know that C11 is not allowed as a requirement. But can we safely assume C99? In particular I want to know if it is OK to use variadic macros as in the following example:

#ifdef DEBUG
#define TRACE(...) printf(__VA_ARGS__)
#endif

[martin-frbg]

I think it should be alright in a MS Windows context, but I'd be more cautious about its use in common code (people stuck with ancient "enterprise" installations of Linux or even dinosaurs running SunOS etc)