Question

I have a very simple question.

in this piece of code when will the value of n be decremented?

#include<stdio.h>
void func(int n)
{ 
  //text//
}

int main()
{
  int n=10;
  func(n--);
  return 0;
}

now when func() is called is the value of n decremented when control comes back to main() or is it decremented at that time only but n=10 is passed to func().
Please explain, also if there is a way to check the value then that will be really helpful.

Answer 1

When a function is called, all it’s arguments are evaluated (in an implementation-defined order) before the function can start – it’s a sequence point. So, after all the arguments are evaluated the function can finally begin.

What this means is that n-- is evaluated and yields the value 10 for the function. At the moment the function has begun n is already 9 but the n parameter of the function hold the value 10.

A simple way to check this:

void func(int n, int *np)
{
    printf("Outside: %d\n", *np);
}

int main(void)
{
    /* ... */
    func(n--, &n);
}