Neat! FYI you are missing include guards. Edit: looking more into it, the header is rather unhygienic: if I include print.h from multiple .c files I break ODR,

Neat! FYI you are missing include guards. Edit: looking more into it, the header is rather unhygienic: if I include print.h from multiple .c files I break ODR, which is undefined behavior. You have variable definitions in a header which is not good. You should guard those variables with a preprocessor define (something like DECLARE_PRINT_VARIABLES or similar) so I can then #define that to 1 in one and only one .c file and then we don’t break ODR.