non-void.c

#include <stdio.h>

void foo(void) {
    static int barf=10;
    barf++;
}

int main()
{
    printf("test: %d\n", (int)foo());
    printf("test: %d\n", (int)foo());
    return 0;
}

/* does not compile on
   on clang 5, gcc-4.8
   
   BUT  prints
    test: 11
    test: 12
   on tcc 0.9.6
 */

void.c

#include <stdio.h>

void foo(void) {
    static int barf=10;
    barf++;
}

int (*foo_)(void) = (int(*)(void))foo;

int main()
{
    printf("test: %d\n", foo_());
    printf("test: %d\n", foo_());
    return 0;
}

/* prints
    test: 11
    test: 12
   on clang 5, gcc-4.8, tcc 0.9.6
 */