[Bug c/49848] New: False positive warning triggered by -Wmaybe-uninitialized

["lacombar at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49848

           Summary: False positive warning triggered by
                    -Wmaybe-uninitialized
           Product: gcc
           Version: 4.5.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: lacombar@gmail.com


Considering the attached reduced-testcase, gcc will trigger the following
warning:

% gcc -m32 -Wall -Os -c -S -o /dev/null foo.c                                   
foo.c: In function 'foo':
foo.c:9:12: warning: 'b' may be used uninitialized in this function

Affected gcc is:

% gcc -v                                     
Using built-in specs.
[...]
Thread model: posix
gcc version 4.5.1 20100924 (Red Hat 4.5.1-4) (GCC)

however, gcc from trunk (as of 20110609) also produces the warning:

/src/x86-64/obj/destdir/bin/x86_64-none-linux-gcc -m32 -Wall -Os -c -S -o
/dev/null foo.c
foo.c: In function 'foo':
foo.c:14:21: warning: 'b' may be used uninitialized in this function
[-Wmaybe-uninitialized]

This warning only shows up at -Os.

Mailing list reference: http://gcc.gnu.org/ml/gcc-help/2011-07/msg00243.html