[Bug c/59668] New: extraneous error messages at -O1, -O2 and -O3 for valid code with string library functions

[Bug c/59668] New: extraneous error messages at -O1, -O2 and -O3 for valid code with string library functions

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59668

            Bug ID: 59668
           Summary: extraneous error messages at -O1, -O2 and -O3 for
                    valid code with string library functions
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The current trunk and older GCC versions reject the following code with odd
error messages at -O1, -O2 and -O3 (but not -O0 and -Os). 

$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 4.9.0 20140103 (experimental) [trunk revision 206321] (GCC) 
$ 
$ gcc-trunk -Wall -Wextra -pedantic -std=c99 -c small.c
$ 
$ gcc-trunk -O0 -c small.c
$ gcc-trunk -Os -c small.c
$ 
$ gcc-trunk -O1 -c small.c
In file included from /usr/include/string.h:637:0,
                 from small.c:1:
small.c:3:5: error: expected identifier or ‘(’ before ‘__extension__’
 int strcmp(const char *, const char *);
     ^
small.c:3:5: error: expected identifier or ‘(’ before ‘)’ token
 int strcmp(const char *, const char *);
     ^
$ 


-----------------------


#include <string.h>

int strcmp(const char *, const char *);
>From gcc-bugs-return-439007-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Fri Jan 03 20:46:52 2014
Return-Path: <gcc-bugs-return-439007-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Delivered-To: listarch-gcc-bugs@gcc.gnu.org
Received: (qmail 5999 invoked by alias); 3 Jan 2014 20:46:51 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
Delivered-To: mailing list gcc-bugs@gcc.gnu.org
Received: (qmail 5969 invoked by uid 48); 3 Jan 2014 20:46:48 -0000
From: "glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/59668] extraneous error messages at -O1, -O2 and -O3 for valid code with string library functions
Date: Fri, 03 Jan 2014 20:46:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 4.9.0
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: glisse at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields:
Message-ID: <bug-59668-4-1ZfC8kKELz@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-59668-4@http.gcc.gnu.org/bugzilla/>
References: <bug-59668-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-SW-Source: 2014-01/txt/msg00149.txt.bz2
Content-length: 203

http://gcc.gnu.org/bugzilla/show_bug.cgi?idY668

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
Well, that's a glibc issue, isn't it?

Btw, you need to provide the preprocessed code.

[Bug c/59668] extraneous error messages at -O1, -O2 and -O3 for valid code with string library functions

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59668

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

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

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Actually this is neither a bug in GCC or glibc.  In C, strcmp can be defined as
a macro and that is what you are getting a macro.
You can fix your code by doing:
int (strcmp)(const char *, const char *);

Instead.

[Bug c/59668] extraneous error messages at -O1, -O2 and -O3 for valid code with string library functions

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59668

--- Comment #3 from Zhendong Su <su at cs dot ucdavis.edu> ---
(In reply to Andrew Pinski from comment #2)
> Actually this is neither a bug in GCC or glibc.  In C, strcmp can be defined
> as a macro and that is what you are getting a macro.

Huh, that's interesting; thanks.  Could you give a pointer where this is
described? 

But again, how come the inconsistent behaviors at different optimization
levels? 

> You can fix your code by doing:
> int (strcmp)(const char *, const char *);
> 
> Instead.

[Bug c/59668] extraneous error messages at -O1, -O2 and -O3 for valid code with string library functions

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59668

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|INVALID                     |DUPLICATE

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Zhendong Su from comment #3)
> (In reply to Andrew Pinski from comment #2)
> > Actually this is neither a bug in GCC or glibc.  In C, strcmp can be defined
> > as a macro and that is what you are getting a macro.
> 
> Huh, that's interesting; thanks.  Could you give a pointer where this is
> described? 

It is described in the C standard but I don't have the exact reference number
for it though.

> But again, how come the inconsistent behaviors at different optimization
> levels? 

Because glibc decides only to implement the macro at -O and above but not when
optimizing for size.

> 
> > You can fix your code by doing:
> > int (strcmp)(const char *, const char *);
> > 
> > Instead.

Anyways this is really a dup of bug 32449.

*** This bug has been marked as a duplicate of bug 32449 ***

[Bug c/59668] extraneous error messages at -O1, -O2 and -O3 for valid code with string library functions

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59668

--- Comment #5 from Zhendong Su <su at cs dot ucdavis.edu> ---
> Because glibc decides only to implement the macro at -O and above but not
> when optimizing for size.

I see; thanks Andrew. 

BTW, is strcmp the only one like this, or there are others?

[Bug c/59668] extraneous error messages at -O1, -O2 and -O3 for valid code with string library functions

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59668

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Zhendong Su from comment #5)
> BTW, is strcmp the only one like this, or there are others?

Almost (if not all) all standard C functions are like this.

[Bug c/59668] extraneous error messages at -O1, -O2 and -O3 for valid code with string library functions

[schwab@linux-m68k.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59668

--- Comment #7 from Andreas Schwab <schwab@linux-m68k.org> ---
7.1.3 Reserved identifiers