#include <stdio.h>

// LOG function to print an integer.
#define logd(x) printf("The value of %s is %d\n", #x, (x))
// When the preprocessor replaces this, `x` in the right-hand-side (RHS)
// will be replaces with the argument to logd(..).
//
// No parentheses or anything extra is assumed.
//
// `#x` will be replaces by the text of the argument to logd(..).

void foo() {
    printf("in foo\n");
}

int main(int argc, char *argv[]) {
    int a = 3;
    logd(a + 2 * 3);
    foo();
    foo();
    foo();
    return 0;
}
/* OUTPUT
The value of a is 3
in foo
in foo
in foo
*/