Bug 15012

Summary: Unexpected behaviour on i--
Product: gcc Reporter: Marcus De Luigi <mdeluigi>
Component: c++Assignee: Not yet assigned to anyone <unassigned>
Status: RESOLVED DUPLICATE    
Severity: minor CC: gcc-bugs
Priority: P3    
Version: 3.3   
Target Milestone: ---   
Host: Target:
Build: Known to work:
Known to fail: Last reconfirmed:

Description Marcus De Luigi 2004-04-19 14:51:36 UTC 
Try that code:
---8<---
int j = 2;
int i = 2;
i = i-- + ++j;
cout << i;
--->8---
The suprising result is that i == 1.
I tried this on pc (intel), powerpc and sparc.

The result is because the compiler does something like:
---8<---
tmp1 = i--;
tmp2 = ++j;
i = i + tmp2;
i = tmp1;
--->8---
(check the asm-code for more details).

That's not what the programer expects.
Comment 1 Andrew Pinski 2004-04-19 14:56:15 UTC 
Invalid as you are modifing i twice without a sequence point inbetween.
i = i-- + ++j;
^    ^
Comment 2 Wolfgang Bangerth 2004-08-05 14:57:08 UTC 
Reopen these bugs...
Comment 3 Wolfgang Bangerth 2004-08-05 15:01:02 UTC 
...mark as duplicate of PR 11751. 

*** This bug has been marked as a duplicate of 11751 ***