Question

1. Is there a performance benefit by passing ints by reference rather than by value ? I say this because if you pass by reference you are creating a 4-byte pointer but if you pass by value you are creating a 4-byte copy of the value anyway. So they both occupy an extra 4-bytes, right ?

2. Is it possible to pass an int literal by reference using a cast: (int *) ? Or do you have to pass a pointer to an int ? See example code below:

   int func1(int *a){
       (*a)++; // edited from comment by Joachim Pileborg
       printf("%i\n", *a);
       return 0;
   }
   
   int func2(int a){
       a++;
       printf("%i\n", a);
       return 0;
   }
   
   int main(void){
       func1(&(int *)5); // an int literal passed by reference using a cast ?
       func2(5);
       return 0;
   }
   

Answer 1

The benefit of passing-by-pointer (there are no references in C) is that a function may update the original int, i.e. return a value in it. There is no performance benefit; rather, passing-by-pointer may slow your program down because the int that is pointed to has to be in addressable memory, so it can’t be in a register.

Note that &(int *)5 does not do what you think it does. (int *)5 casts the value 5 to a pointer, interpreting it as a memory address. The & would give that pointer’s address, except that taking the address of a temporary is illegal. You probably meant

int i = 5;
func1(&i);