Re: [avr-gcc-list] WinAVR - gcc 3.4.6 - AVR Studio - DuoCore PC - Stackpointer problem

[Steffen Rose]

Hello,

On Saturday 25 November 2006 23:15, Joerg Wunsch wrote:
> Steffen Rose <address@hidden> wrote:
> > wrong code:
> >     PUSH R17
> >     PUSH R28
> >     PUSH R29
> >     IN R30,0x3D
> >     IN R31,0x3E
> >     SUBI R30,0x4A
> >     SBCI R31,0x10
> >     STD Z+0,R1
> >     LDS R24,0x500
> >     TST R24
> >     BREQ PC+0x03
> >     CALL 0x12A
> >
> > The Subtraction 0x104A from the Stackpointer is very high.
>
> That would suggest you've been declaring a *lot* of local
> variables.
>
> Is this perhaps without optimization (-O0), and the other case
> uses optimizations?  In that case, it's possible the compiler
> optimized all your local variables away because they are not
> needed.  But still, the error is in your code if you are
> trying to reserve more variables than you've got RAM (stack in
> that case) available.

That's not so simple. It's a function without parameters and only 
two pointer and a unsigned char local variable. In both cases 
the Optimization is -Os -mcall-prologues. 

Is it possible to see all used options within the listing files? 
I'm not sure, if the options, that I see in the AVR studio 
command line are all used options. Within the *.i and *.s files 
the used options are not included. :-(

Do the avr-gcc know an optimization, that the stack frame for all 
called functions are created within the first called function?

Thank you for your ideas.
-- 
Regards
Steffen Rose