Re: Handling pre-increment and post-increment in GCC

[Andrew Haley <aph at redhat dot com>]

Manjunath B S writes:

 >     I am trying to understand how GCC handles this piece of code, but
 > unfortunately the behaviour is different on different architectures
 > =====================================================
 > #include < stdio.h>
 > 
 > int main(void)
 > {
 >     int i = 2;
 > 
 >     return printf("Post increment : %d, Pre increment : %d\n", i++, ++i);
 > }
 > =====================================================
 > 
 > On Powerpc (Powerbook G4) this gives
 > %%%%%%%%%%%%%%%%%%%
 > Post increment : 2, Pre increment : 4
 > 
 > however on Intel machines this gives
 > %%%%%%%%%%%%%%%%%%%
 > Post increment : 4, Pre increment : 2
 > 
 > On MIPS & ARM, the behaviour is different as well.
 > 
 > Can anyone please explain the same?? Also can anyone please point me
 > the direction where I should look in the GCC Internals for a clear
 > understanding??

It doesn't matter, because Your code is undefined on any C compiler on
any machine.  See C99, Section 6.5 Para. 2.

Andrew.