[Bug c/49068] New: Failure to auto-cast in expression, results in broken code

[Bug c/49068] New: Failure to auto-cast in expression, results in broken code

[thomas.evans at nrl dot navy.mil]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49068

           Summary: Failure to auto-cast in expression, results in broken
                    code
           Product: gcc
           Version: 4.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: thomas.evans@nrl.navy.mil


Subject:

Target: i686-apple-darwin10
Configured with: /var/tmp/gcc/gcc-5666.3~6/src/configure --disable-checking
--enable-werror --prefix=/usr --mandir=/share/man
--enable-languages=c,objc,c++,obj-c++
--program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib
--build=i686-apple-darwin10 --program-prefix=i686-apple-darwin10-
--host=x86_64-apple-darwin10 --target=i686-apple-darwin10
--with-gxx-include-dir=/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Apple Inc. build 5666) (dot 3)

=========================================================

Predicate:

the code:

  int gnome, jape[20];
  char buff[888];

  gnome = sscanf(buff," %d %d %d %d %d %d %d %d %d",jape+0, jape+1, jape+2, &
    jape+3, jape+4, jape+5, jape+6, jape+7, jape+8);

generates the following warning:

warning: format '%d' expects type 'int *', but argument 6 has type 'int
(*)[20]'

also, the code does not work properly -- the values in jape[] are not the same
as those in the buff[] array.

The cause apears to be the expression jape+0 (or maybeso jape+5, but that makes
much less sense from my naive perspective) being prematurely optimized by 
removal of the +0, which would otherwise force a quiet cast of jape from 
'int (*)[20]' to 'int *'.

[Bug c/49068] Failure to auto-cast in expression, results in broken code

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49068

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-05-19 18:17:17 UTC ---
It does say which argument too: "argument 6".

[Bug c/49068] Failure to auto-cast in expression, results in broken code

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49068

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-05-19 18:16:53 UTC ---
&jape+3 is the issue.

[Bug c/49068] Failure to auto-cast in expression, results in broken code

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49068

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

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

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-05-20 09:40:25 UTC ---
&jape + 3 doesn't do what you think.