[Bug c/38037] New: false uninitialized warnings when using a pointer as a guard

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

With the testcode below I get an uninitialized use warning.
There should be no warning since foobar is always assigned when (!bar), and
foobar is only used when (!bar). 
bar is an argument to the function and nothing changes it, and it is not
aliased.

$ gcc -O2 -Wall -c foo.c
foo.c: In function ?foo?:
foo.c:6: warning: ?foobar? may be used uninitialized in this function

This happens on both 4.3.2 and trunk
$ gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.2-1'
--with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.3
--program-suffix=-4.3 --enable-clocale=gnu --enable-libstdcxx-debug
--enable-objc-gc --enable-mpfr --enable-cld --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.3.2 (Debian 4.3.2-1)

$ gcc_inst/bin/gcc -v
Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc/configure --disable-multilib --disable-static
--prefix=/home/edwin/gcc_inst/ --enable-languages=c,c++
Thread model: posix
gcc version 4.4.0 20081103 (experimental) [trunk revision 141547] (GCC)


-- 
           Summary: false uninitialized warnings when using a pointer as a
                    guard
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: edwintorok at gmail dot com
 GCC build triplet: x86_64-linux-gnu
  GCC host triplet: x86_64-linux-gnu
GCC target triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38037