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Date: Wed, 25 Aug 2004 21:13:00 -0000
From: "nomura at netapp dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Message-ID: <20040825211324.17191.nomura@netapp.com>
Reply-To: gcc-bugzilla@gcc.gnu.org
Subject: [Bug c/17191] New: address taken prevents uninitialized variable warning
X-Bugzilla-Reason: CC
X-SW-Source: 2004-08/txt/msg02683.txt.bz2
List-Id: <gcc-bugs.sourceware.org>

Compiling this code with -O -Wall should warn that "i" is used without
being initialized.  The presence of "p = &i" stops this warning
from being issued, but the address is not exposed in a way that could
affect i.  (No path from the address taken to the use, and the variable 
is local).  If the uninit warning could be strengthened it would have
real benefits.

-- Source code:

int *p;

void foo ()
{
        int i;
        if (i < 100)
                return;
        p = &i;
}

-- Command line:

[gecko]$ xgcc-3.4 -v -c -O2 a.c -Wall -Werror
Reading specs from /u/nomura/dl/gcc-3.4.1_linux/gcc/specs
Configured with: ../gcc-3.4.1/configure --enable-languages=c,c++
--prefix=/x/sim/nomura/root.linux/gcc-3.4.1
Thread model: posix
gcc version 3.4.1
 /u/nomura/dl/gcc-3.4.1_linux/gcc/cc1 -quiet -v -iprefix
/u/nomura/dl/gcc-3.4.1_linux/gcc/../lib/gcc/i686-pc-linux-gnu/3.4.1/ -isystem
/u/nomura/dl/gcc-3.4.1_linux/gcc/include a.c -quiet -dumpbase a.c
-mtune=pentiumpro -auxbase a -O2 -Wall -Werror -version -o /tmp/ccN7EB39.s
ignoring nonexistent directory
"/u/nomura/dl/gcc-3.4.1_linux/gcc/../lib/gcc/i686-pc-linux-gnu/3.4.1/include"
ignoring nonexistent directory
"/u/nomura/dl/gcc-3.4.1_linux/gcc/../lib/gcc/i686-pc-linux-gnu/3.4.1/../../../../i686-pc-linux-gnu/include"
ignoring nonexistent directory
"/x/sim/nomura/root.linux/gcc-3.4.1/lib/gcc/i686-pc-linux-gnu/3.4.1/../../../../i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /u/nomura/dl/gcc-3.4.1_linux/gcc/include
 /usr/local/include
 /x/sim/nomura/root.linux/gcc-3.4.1/include
 /x/sim/nomura/root.linux/gcc-3.4.1/lib/gcc/i686-pc-linux-gnu/3.4.1/include
 /usr/include
End of search list.
GNU C version 3.4.1 (i686-pc-linux-gnu)
        compiled by GNU C version 3.2 20020903 (Red Hat Linux 8.0 3.2-7).
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
 /x/sim/nomura/root.linux/gcc-3.4.1/lib/gcc/i686-pc-linux-gnu/3.4.1/../../../../i686-pc-linux-gnu/bin/as
--traditional-format -V -Qy -o a.o /tmp/ccN7EB39.s
GNU assembler version 2.15 (i686-pc-linux-gnu) using BFD version 2.15
[gecko]$

-- 
           Summary: address taken prevents uninitialized variable warning
           Product: gcc
           Version: 3.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: nomura at netapp dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17191