[Bug c/50669] New: no warning for unused globals

[Bug c/50669] New: no warning for unused globals

[jg at jguk dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50669

             Bug #: 50669
           Summary: no warning for unused globals
    Classification: Unclassified
           Product: gcc
           Version: 4.5.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jg@jguk.org


I see unused warning for item on stack, but not global variale that is unused.
Could gcc also give warnings for unused globals?

jon@laptop:~$ gcc -Wextra -Wunused -Wall -o main main4.c
main4.c: In function ‘main’:
main4.c:9:6: warning: unused variable ‘unused_flag’


Example program follows:

// gcc -Wextra -Wunused -Wall -o main main4.c


int unused_int;


int main(void)
{
    int unused_flag;

    return 0;
}

[Bug c/50669] no warning for unused globals

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50669

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-10-09 11:38:34 UTC ---
The variable is exported, so it is not known to be unused.

[Bug c/50669] no warning for unused globals

[jg at jguk dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50669

--- Comment #2 from Jon Grant <jg at jguk dot org> 2011-10-09 16:44:18 UTC ---
I could understand this for libraries. However, when linking as an executable
binary, could the global really be still exported?

[Bug c/50669] no warning for unused globals

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50669

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-10-09 19:34:48 UTC ---
(In reply to comment #2)
> I could understand this for libraries. However, when linking as an executable
> binary, could the global really be still exported?

Yes.  In fact this is how plugins work in GCC.

[Bug c/50669] no warning for unused globals

[jg at jguk dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50669

--- Comment #4 from Jon Grant <jg at jguk dot org> 2011-10-10 22:41:22 UTC ---
Ok. That makes sense. I confirmed by modifying the test, and having "static int
unused_int;" which gives a warning that it is unused at global scope.