[Bug c++/64332] gcc/g++ handles system_header differently

["a3at.mail at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64332

--- Comment #3 from Azat <a3at.mail at gmail dot com> ---
On Tue, Dec 16, 2014 at 07:50:48PM +0300, Azat Khuzhin wrote:
> > --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
> > I don't think it is system header which is being handled differently, rather I
> > think it is warning for attribute is being handled differently.
> 
> Maybe... I didn't check this.

I've checked this and you are right:
$ head main.c c-impl.h  # the same is in attach
==> main.c <==
#include "c-impl.h"

==> c-impl.h <==
#pragma GCC system_header

static inline int foo(int foo)
{
}

$ gcc -Wall -Wextra -Wpedantic -Wattributes -c main.c
$ g++ -Wall -Wextra -Wpedantic -Wattributes -c main.c

Now drop system_header:
$ head main.c c-impl.h 
==> main.c <==
#include "c-impl.h"

==> c-impl.h <==
static inline int foo(int foo)
{
}

$ gcc -Wall -Wextra -Wpedantic -Wattributes -c main.c
In file included from main.c:1:0:
c-impl.h: In function âfooâ:
c-impl.h:3:1: warning: no return statement in function returning non-void
[-Wreturn-type]
 }
 ^
c-impl.h:1:27: warning: unused parameter âfooâ [-Wunused-parameter]
 static inline int foo(int foo)
                           ^
$ g++ -Wall -Wextra -Wpedantic -Wattributes -c main.c
In file included from main.c:1:0:
c-impl.h: In function âint foo(int)â:
c-impl.h:3:1: warning: no return statement in function returning non-void
[-Wreturn-type]
 }
 ^
c-impl.h: At global scope:
c-impl.h:1:27: warning: unused parameter âfooâ [-Wunused-parameter]
 static inline int foo(int foo)
                           ^