[Bug c/53480] New: warning "may be used uninitialized" issued with -m32 but not with -m64

["gbburkhardt at verizon dot net" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53480

             Bug #: 53480
           Summary: warning "may be used uninitialized" issued with -m32
                    but not with -m64
    Classification: Unclassified
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: gbburkhardt@verizon.net


For the following program, a warning is issued with "-m32", but not with
"-m64".

armis@armis-00:~$ gcc -c -O2 -g -Wall -m32 -std=gnu99 tt.c
tt.c: In function ‘sub’:
tt.c:18:29: warning: ‘v0.minValue’ may be used uninitialized in this function
[-Wuninitialized]
tt.c:21:29: warning: ‘v0.maxValue’ may be used uninitialized in this function
[-Wuninitialized]
armis@armis-00:~$ gcc -c -O2 -g -Wall -m64 -std=gnu99 tt.c
armis@armis-00:~$

#include <stdio.h>
typedef struct {
    double minValue, maxValue;
} Range;

void getNewRange(Range*);

void sub() 
{
    Range v0, v1;

    for (int i=0; i < 2; i++) {
        getNewRange(&v1);
        if (i == 0) {
            v0.minValue = v1.minValue;
            v0.maxValue = v1.minValue;
        } else {
            if (v0.minValue > v1.minValue)
                v0.minValue = v1.minValue;

            if (v0.maxValue < v1.maxValue)
                v0.maxValue = v1.maxValue;
        }
    }

    printf("min=%f, max=%f\n", v0.minValue, v0.maxValue);   
}

armis@armis-00:~$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.6.1-9ubuntu3' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++,go --prefix=/usr
--program-suffix=-4.6 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-plugin
--enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3)