TR : Possible GCC bug on m68k

[etienne.fortin at sensio.tv]

Hi Thomas,
Isn't it strange to work on unsigned char and getting result on int from
the ~ operator? What's the rational behind this? In a typed language, I
expect computing to be done on the type I specify, not on some hidden
assumption by the language.

Anyway, if it's the programmer's fault, then I'll just take note and don't
do that mystake again :)

Etienne



> Hi,
>
> I tried Joels test with a gcc-2.8.1. It also generated code with
> a "long" (32 bit) compare. My idea about that: Wouldn't the "~"
> operator generate an "int" result, forcing the comparision to be
> done with "int" (=32 bit) size? This does not make sense in that
> situation, but this is an issue for the programmer (Etienne) not
> the compiler. Am I totally wrogn with this?
>
> wkr, and good night :-)
> Thomas.
>
>
>> Yes, it seems to match what I'm getting.
>>
>>
>> -----Message d'origine-----
>> De : Joel Sherrill <joel at OARcorp.com> [mailto:joel.sherrill at OARcorp.com]
>>
>> Envoyé : 2 novembre, 2004 17:01
>> À : Etienne Fortin
>> Cc : rtems-users at rtems.com
>> Objet : Re: RE : RE : TR : Possible GCC bug on m68k
>>
>>
>> Etienne Fortin wrote:
>> > The one that comes with RTEMS-4.6.1.
>> >
>>
>> That would have been a gcc 3.2 series.  I now have an
>> example which is pretty simple:
>>
>> typedef struct {
>>    unsigned char number;
>> } pkt;
>>
>> unsigned int f( int i );
>> int g( pkt *packet )
>> {
>>    unsigned char comp;
>>
>>    packet->number = (unsigned char)f(1);
>>    comp = (unsigned char)f(2);
>>    if (packet->number != ~comp)
>>       return 1;
>>    return 0;
>> }
>> /* packet->number = 0 and comp = 0xFF. */
>>
>>
>> I tried it with the latest 4.6.2 tools and my current
>> gcc 3.3.5 tools for 4.7 and it shows the same disassembly
>> at both -02 and -O4.
>>
>> /opt/rtems-4.7/bin/m68k-rtems4.7-gcc -S -O4 m68k1.c
>> /opt/rtems-4.6/bin/m68k-rtems-gcc -S -O2 m68k1.c
>>
>> Does this example match what you think is happening?
>>
>> --joel
>>
>
> --------------------------------------------
> IMD Ingenieurbuero fuer Microcomputertechnik
> Thomas Doerfler           Herbststrasse 8
> D-82178 Puchheim          Germany
> email:    Thomas.Doerfler at imd-systems.de
> PGP public key available at: http://www.imd-
> systems.de/pgp_keys.htm
>
>