RE: [avr-gcc-list] Gcc bug??

[Brian Cuthie]

I will try to build something that demonstrates the problem. Thanks.

-brian 

> -----Original Message-----
> From: address@hidden 
> [mailto:address@hidden On Behalf Of Klaus Rudolph
> Sent: Wednesday, March 03, 2004 1:45 AM
> To: address@hidden
> Cc: address@hidden
> Subject: Re: [avr-gcc-list] Gcc bug??
> 
> Brian Cuthie wrote:
> > 
> > I'm having some problems with an app that uses AvrX and gcc 
> (v. 3.3.1) 
> > on an ATmega16. In the interrupt routine for the TWI  I 
> write a static 
> > with a code that indicates its current state. In an effort 
> to debug a 
> > different problem I compiled the code without any optimization.
> > 
> > While I did discover the original problem I had been hunting, I 
> > started to see some very unreliable behavior with the TWI. 
> After some 
> > investigation I determined that the state variable 
> (mentioned above) 
> > was getting written with an unreasonable value (not a valid state). 
> > The correct state value that should have been written into the 
> > variable is "0". Further experiments revealed that memory 
> corruption 
> > (at least directly into the variable's memory location) was 
> not the problem.
> > 
> > What I then determined is that the "0" register (r1) 
> contained the value 8!
> > This, not coincidentally (and looking at the disassembled code) is 
> > exactly the value that's being incorrectly written into the 
> static state variable.
> > Interestingly, turning on any level of optimization seems 
> to fix it, 
> > at least as observed by the TWI port handler not hanging.
> > 
> > I was wondering if anyone else has seen anything like this, 
> or has any 
> > advice or suggestions.
> 
> Can we have a look inside the code itself? Please cut all 
> unneeded stuff away and send us the source code and the 
> Makefile with the good and the corrupt compile options. It is 
> a bit difficult to say: Is it possible that gcc has a bug or 
> not :-) Please comment the code that the corrupt lines can be 
> found fast.
> 
> Thanks
>       Klaus
> 


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