Can I Use post increment in function return in C?

Question

can I use post-increment in a function return in C like this?

int meta_solve() {    
  //some codes
  return metaData[head++]; //head is global variable
}

I asking this question because it showing the different results on windows and mac. thanks for your attention. have a great day!

It depends on how you're calling the function. If you're calling the function twice with no sequence point between them, the order that they're called is not specified, so the order of the increments will change. — Barmar, Jun 05 '21 at 16:28
@Barmar While that is true, it doesn't change that post-increment in the return statement is fine. — Support Ukraine, Jun 05 '21 at 16:34
not a windows or mac thing but one compiler from another, show the dissassembly from each one you think varies — old_timer, Jun 05 '21 at 16:39
@4386427 Right, it would be just as much of a problem if the increment were in its own statement. — Barmar, Jun 05 '21 at 18:28

score 2 · Accepted Answer · answered Jun 05 '21 at 16:31

2

Yes, that will work.

The return will not happen until the expression metaData[head++] is fully evaluated so the (global) variable head is incremented before the function returns.

answered Jun 05 '21 at 16:31

Support Ukraine

42,271
4
38
63

Actually, it is a defect in the C standard that nothing in the normative text states there is a sequence point after a `return` statement. Theoretically, the increment is allowed to happen after the function returns. If the call is inside a larger expression , the increment may not be sequenced with respect to other things in the expression. – Eric Postpischil Jun 05 '21 at 19:42

Can I Use post increment in function return in C?

1 Answers1