Hello, https://gcc.gnu.org/gcc-5/porting_to.html states "Typically, this macro is used as in the following: #if !defined __STDC_VERSION__ || __STDC_VERSION__ < 199901L /* ... */ #else # include <stdint.h> #endif " I think it is unnecessary to test for the existence of __STDC_VERSION__ because N1256 6.10.1p4 states "all remaining identifiers [...] are replaced with the pp-number 0" Therefore #if __STDC_VERSION__ < 199901L would work as expected, even when __STDC_VERSION__ is undefined. (As the constant-expression would be false.) Regards.
