printf conversion specifier for _Bool?

Question

With printf(), I can use %hhu for unsigned char, %hi for a short int, %zu for a size_t

Answer 1

Until C99, bool was not apart of standard C, and thus did not exist as a printf modifier. C99, defined _Bool (which you are using) to be an integer, thus you should be fine casting it as an integer to display (at least from a machine perspective). Alternatively, you could do something like:

printf("%d",foo?1:0);