target/10733: Modulus bug

[jbright@winfordeng.com]

>Number:         10733
>Category:       target
>Synopsis:       Modulus bug
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Sat May 10 15:36:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     John Bright
>Release:        avr-gcc (GCC) 3.2.3 20030221 (Debian prerelease)
>Organization:
>Environment:
Linux host system, AVR cross-compiler for Atmel AT90S8535
>Description:
C Source code:
--------------------------------
int t1;

t1=2;
t1=(t1+40)%30;
--------------------------------
This results in t1 having a value of 42.

Compile options:
avr-gcc -g -Os -Wall -Wstrict-prototypes -mmcu=at90s8535

I found this bug while using avr-gcc 3.0.3 (in Debian stable).  I tried out with 3.2.3 and the same bug still exists.
>How-To-Repeat:

>Fix:
In the above example, the bug can be worked-around by doing the modulus separately:

t1=2;
t1=t1+40;
t1%=30;
>Release-Note:
>Audit-Trail:
>Unformatted: