inappropriate "discards qualifiers from pointer target type" warning

[John Breitenbach]

Hi,
  I think I'm seeing a bug with gcc which came in between 4.1.1 and 4.2.

I've got a function which takes a const void * and casts it to a void * 
when passing it to another function.  ONLY if the target function is in 
the same module, I get the subject warning.  A simple extern declaration 
does not produce any warnings.  Also, I see it at >= O3 or Os.  This 
does not show up at O2.

You will notice that without the explicit cast, I get the warning 
TWICE.  Thanks for any advice.

cat slab.c
void __cache_free(void *objp) { return; }
void kfree(const void *objp) { __cache_free((void *)objp); }

/* No warning @ O2 */
/m/btools/futures/next/builds/wip-4327-rt47353/ix86-Linux-RHEL4/i686-pc-linux-gnu_gcc-4.2.3/bin/gcc 
-c -O2 -Wall slab.c

/* One warning @ O3 */
 /m/btools/futures/next/builds/wip-4327-rt47353/ix86-Linux-RHEL4/i686-pc-linux-gnu_gcc-4.2.3/bin/gcc 
-c -O3 -Wall slab.c
slab.c: In function 'kfree':
slab.c:2: warning: passing argument 1 of '__cache_free' discards 
qualifiers from pointer target type

/* Now removing the explicit cast when calling __cache_free() */
 /m/btools/futures/next/builds/wip-4327-rt47353/ix86-Linux-RHEL4/i686-pc-linux-gnu_gcc-4.2.3/bin/gcc 
-c -O2 -Wall slab.c
slab.c: In function 'kfree':
slab.c:2: warning: passing argument 1 of '__cache_free' discards 
qualifiers from pointer target type

/* and get the warning TWICE at O3 */
/m/btools/futures/next/builds/wip-4327-rt47353/ix86-Linux-RHEL4/i686-pc-linux-gnu_gcc-4.2.3/bin/gcc 
-c -O3 -Wall slab.c
slab.c: In function 'kfree':
slab.c:2: warning: passing argument 1 of '__cache_free' discards 
qualifiers from pointer target type
slab.c:2: warning: passing argument 1 of '__cache_free' discards 
qualifiers from pointer target type


 /m/btools/futures/next/builds/wip-4327-rt47353/ix86-Linux-RHEL4/i686-pc-linux-gnu_gcc-4.2.3/bin/gcc 
--version
gcc (GCC) 4.2.3
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.