gcc not finding all occurences of potentially undefined values?

[Daniel Kabs <daniel.kabs@xxxxxx>]

Hello there,

after upgrading to a new version, gcc issues warnings on lines like

  a[i] = i++;
  i = i++;
  *p++ = func(*p);

e.g.
"test_increment.c:19: warning: operation on `i' may be undefined"

I take it, this is because of the C standard saying, that if I have an 
expression and somewhere in that expression, I use an increment 
(decrement) operator on a variable, I can not mention that variable 
elsewhere in the expression.

But why does gcc not warn about this code

  s.a = s.a++;
  p->a = p->a++;


IMHO, these lines also infringe upon the above mentioned rule or did I 
miss something important?

Cheers
Daniel