Re: Question about gcc-3.3.3 and __attribute__ usage

[Tom Williams <tomdkat@xxxxxxxxxxx>]

Ian Lance Taylor wrote:

> Tom Williams <tomdkat@xxxxxxxxxxx> writes:
>
>  
>
> > Apparently, the Linux 2.6 kernel headers were changed to use
> > __attribute_const__ syntax instead of __attribute__((const)):
> >    
>
> __attrbute_const__ is not valid gcc syntax.
>
> However, it is a preprocessor macro defined by the Linux sources which
> expands into valid gcc syntax.  I think the file is
> include/linux/compiler.h, or some such.
>
> Ian
>
>  
Thanks!  :)

I found the following in /usr/include/linux/compiler.h:


#ifndef __attribute_const__
# define __attribute_const__    /* unimplemented */
#endif


Which I looks like it's trying to define __attribute_const__ to nothing 
so it will be automatically removed from this:

static __inline__ __attribute_const__ int foo()

resulting in:

static __inline__ int foo()

So, I wrote a test prog to see if this is actually the case:

tom@linux:~$ cat tom.c
#include <linux/compiler.h>

#ifdef __attribute_const__
#error It is defined!
#endif

static __inline__ __attribute_const__ int foo()
{
       return 0;
}

int main(int argc, char **argv)
{
       foo();

       return 0;
}
tom@linux:~$

and this is what happens when I compile it:

tom@linux:~$ make tom
cc     tom.c   -o tom
tom.c:7: error: syntax error before "int"
make: *** [tom] Error 1
tom@c71414-a:~$ gcc -E tom.c
# 1 "tom.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "tom.c"
# 1 "/usr/include/linux/compiler.h" 1 3 4
# 2 "tom.c" 2





static __inline__ __attribute_const__ int foo()
{
       return 0;
}

int main(int argc, char **argv)
{
       foo();

       return 0;
}
tom@linux:~$ cc --version
cc (GCC) 3.3.3
Copyright (C) 2003 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.

tom@linux:~$

Any idea on what might be up?  I guess the pre-processor isn't replacing 
the __attribute_const__ like it should???

Thanks...

Peace...

Tom