Name
_Generic - type-generic selectionSynopsis
_Generic( expression ", type1: " e1 ", " "... /*" \", default: " "e */" );
Description
_Generic() evaluates the path of code under the type selector that is compatible with the type of the controllingexpression, or default: if no type is compatible. expression is not evaluated.
This is especially useful for writing type-generic macros, that will behave differently depending on the type of the argument.
Standards
C11.History
C11.Examples
The following program demonstrates how to write a replacement for the standard imaxabs(3) function, which being a function can't really provide what it promises: seamlessly upgrading to the widest available type.#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#define my_imaxabs _Generic(INTMAX_C(0), \e
long: labs, \e
long long: llabs \e
/* long long long: lllabs */ \e
)
int
main(void)
{
off_t a;
a = -42;
printf("imaxabs(%jd) == %jd\en", (intmax_t) a, my_imaxabs(a));
printf("&imaxabs == %p\en", &my_imaxabs);
printf("&labs == %p\en", &labs);
printf("&llabs == %p\en", &llabs);
exit(EXIT_SUCCESS);
}