Re: [avr-gcc-list] ... Serious Bug in gcc head 4.1 and 4.0 .

[Brian Dean]

On Thu, Jun 09, 2005 at 07:10:47PM +0200, Haase Bjoern (PT-BEU/EMT) * wrote:

> Today I have identified today a serious "wrong code" bug in the gcc
> 4.x.x family. The error I have seen shows up in the context of
> frame-pointer removal: In a situation where gcc would need two stack
> slots to place local variables, I have observed that both, a gcc 4.0
> snapshot and present head cvs 4.1 ...
> 
> 1.) Place one local automatic Pmode variable on the stack
> 2.) Overwrite the frame pointer in the body of the function
> 3.) Try to access the variable by using the overwritten frame pointer.

I too have at least one relatively large program that spontaneously
resets (an ATmega128) when using GCC 4.0.0 with -O but runs as
expected without optimization enabled.  I don't know if it's caused by
the same problem or not, but gcc 3.4.3 works fine with it.
Unfortuneatly the program that exhibits this behaviour is fairly large
and I've not yet been able to isolate it yet to a simple example.

-Brian
-- 
Brian Dean
http://www.bdmicro.com/