[coldfire-gnu-discuss] Re: systemcall select() seems to overwrite variables on the stack

[Tom Evans <thomasaevans@xxxxxxxxxxxxxxx>]

On 10/12/10 2:33 AM, Andreas Wehrmann wrote:
> A colleague and I managed to write a test program that reproduces
> a problem related to calling select().
> ...
> ldi_dev.c  before select_fd=67 | nfds = 68
> ldi_dev.c  before select_fd=67 | nfds = -2141341700

Which is 0x805DB7FC. That may point to the problem.

What does that point to in your map file? You should be able to find 
from the map (or with a bit of debugger help) what data structures are 
there. If that doesn't help, can you set a watchpoint on that in your 
debugger (or gdb) and see what accesses it? Or stop in the debugger and 
dump around that address to see what it looks like.

Less likely:

http://forums.freescale.com/t5/68K-ColdFire-reg-Microprocessors/5208-SDR-SDRAM-MOVEM-L-Instruction-Whacks-Stack-otherwise-SDRAM/m-p/3152

That was caused by setting the SDRAM controller to do an 8-byte burst 
where the hardware only supported 4, and this was only triggered by the 
movem.l. I think I've also heard of a similar problem where the stack 
pointer isn't initialised to a multiple of 4 bytes on some 
architectures. Check the stack pointer value when it fails. It might be 
16-bit-odd.

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Tom Evans