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Re: [avr-gcc-list] WinAVR 20050214 (gcc 3.4.3) and optimizer bug.

From: Joerg Wunsch
Subject: Re: [avr-gcc-list] WinAVR 20050214 (gcc 3.4.3) and optimizer bug.
Date: Mon, 9 May 2005 21:01:48 +0200 (MET DST)

Vesa Jääskeläinen <address@hidden> wrote:

> Thank you for this information. This indeed seems to cure the
> problem in this case. But shouldn't this be default for AVR ?

I'm not sure.  On the AVR, memory address 0 is an alias for r0.  Thus,
by dereferencing a NULL pointer, you're touching whatever r0 (rather
r0/r1) points to.  As this can touch anywhere (including memory-mapped
IO devices), the behaviour is completely undefined, and you should
probably avoid that kind of program anyway.

However, the assumption that a pointer is not NULL just because the
program still runs at a certain point is for sure wrong for the AVR,
so I think you should write a bug report for this.

cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)

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