test_generics.c

#include <stdio.h>

/* does weird behavior in clang. it ignores the char* rule and casts char*
parameters to ints. no clue why. the uncommented version has the fix, and i'm
not sure why it works.

#define abs(x) _Generic((x), \
        long int: absl,\
        double: absd, \
        char*: abss, \
        default: absi \
        )(x)
*/

#define abs(x) _Generic((0, x), \
        long int: absl,\
        double: absd, \
        char*: abss, \
        default: absi \
        )(x)

void absl(long x) { printf("this is a long: %ld\n", x); }
void absd(double x) { printf("this is a double: %f\n", x); }
void abss(char *x) { printf("no strings in absolute value funcs\n"); }
void absi(int x) { printf("this is an int: %d\n", x); }

int main(void)
{
    abs(1L);
    abs(3.14);
    abs("hello");
    abs(18);
}