From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Lunn <andrew.lunn@ascom.ch>
To: Jonathan Larmour <jlarmour@redhat.com>
Cc: Andrew Lunn <andrew.lunn@ascom.ch>, "Trenton D. Adams" <tadams@theone.dnsalias.com>, "'eCos Discussion'" <ecos-discuss@sourceware.cygnus.com>
Subject: Re: [ECOS] Network programming for eCos under linux
Date: Wed, 08 Aug 2001 06:51:00 -0000
Message-id: <20010808155117.E3658@biferten.ma.tech.ascom.ch>
References: <019301c11f92$0aad4b60$090110ac@TRENT> <20010808093506.B3658@biferten.ma.tech.ascom.ch> <3B713E35.B7C21FA@redhat.com>
X-SW-Source: 2001-08/msg00221.html

> I'm not sure this is a compiler bug - I would suspect the linux compiler
> can't access non-aligned memory either, but at a guess the kernel catches
> the exception and emulates it for you. If that is the case, it's best
> avoided as performance would suck.

I don't remeber the exact details. The code was something like...

static int 
func(char * msg, char * name ; short rr_type) {

 char *ptr;
 int len;
        
 strcpy(msg,name);
 ptr = msg + strlen(name);

 *ptr++ = ((char *)&rr_type)[0];
 *ptr++ = ((char *)&rr_type)[1];
 
 len = ptr - msg;

 return len;
}
 
Maybe i don't have the casts correct. Anyway, i found the ptr was not
being incremented when ptr was not word aligned before the first
*ptr++ operation. This could happen because name can be any length. It
worked fine on i386, but not on arm-elf. To me, this is a compile
bug. I got around it by using shifts and ands instead of casts and
array access.


        Andrew