-fvia-c doesn't work

It seems that I am unable to use -fvia-c with ghc, because it gives
some C header file conflicts.  Here is the observable problem:

    $ ghc-6.2.1 -c -fvia-c /tmp/ghcbug.hs
    In file included from /usr/include/stdlib.h:414,
                     from /usr/malcolm/local/lib/ghc-6.2.1/include/Stg.h:200,
                     from /tmp/ghc1723.hc:3:
    /usr/include/sys/types.h:190: conflicting types for `int8_t'
    stdint.h:33: previous declaration of `int8_t'

It seems to happen for all versions of ghc, from 5.04.3 right up to
a recent 20040926 snapshot.  The gcc visible in my PATH is 3.2.2,
and I'm using Slackware 9 Linux.  Using gcc directly to compile a
simple C program like

    #include <stdint.h>
    #include <stdlib.h>
    int8_t test = 0;

doesn't cause any error.  It doesn't matter whether ghc was installed
from a binary package, or if I compile it myself from the src tarball.

Anybody got any ideas?  Is it a gcc problem or a ghc one?  The only
reason I noticed this is because I tried using -O optimisation today
for the first time in ages, and -O implies -fvia-c.

Regards,
    Malcolm