Question

For example:

#include <stdio.h>

typedef void (* proto_1)();
typedef void proto_2();

void my_function(int j){
    printf("hello from function. I got %d.\n",j);
}

void call_arg_1(proto_1 arg){
    arg(5);
}
void call_arg_2(proto_2 arg){
    arg(5);
}
void main(){
    call_arg_1(&my_function);
    call_arg_1(my_function);
    call_arg_2(&my_function);
    call_arg_2(my_function);
}

Running this I get the following:

> tcc -run try.c
hello from function. I got 5.
hello from function. I got 5.
hello from function. I got 5.
hello from function. I got 5.

My two questions are:

• What is the difference between a function prototype defined with (* proto) and one defined without?
• What is the difference between calling a function with the reference operator (&) and without?

Answer 1

There is no difference. For evidence see the C99 specification (section 6.7.5.3.8).

“A declaration of a parameter as ‘‘function returning type’’ shall be adjusted to ‘‘pointer to
function returning type’’, as in 6.3.2.1.”