c_generic_expression.c

#include <stdio.h>

/*
 * GCC spits out warnings that I think it shouldn’t as the standard
 * says that “None of the expressions from any other generic
 * association of the generic selection is evaluated.” (9899:2011
 * 6.5.1.1)
 */
/* #define p(x) _Generic(x, long: printf("%ld\n", x), int: printf("%d\n", x), const char *: printf("%s\n", x), char *: printf("%s\n", x))*/
/*
 * But, anyway, it can be written more simply, readably, and
 * without making GCC mad by just generifying over the format
 * parameter itself.
 */
#define p(x) printf(_Generic(x, int: "%d\n", long: "%ld\n", char *: "%s\n"), x)

int main(int argc, const char *const argv[])
{
  p("hi");
  p(23);
  return 0;
}

scriptfile

~ $ gcc -Wall -o c_generic_expression c_generic_expression.c 
~ $ ./c_generic_expression 
hi
23
~ $