[Bug middle-end/17534] New: gcc fails to diagnose suspect expressions that have incompatible bit masks

["trt at acm dot org" <gcc-bugzilla at gcc dot gnu dot org>]

The expressions (z & 2) == 4 and (z | 2) == 4 are always false. When these
appear in programs it is almost always unintended, but gcc fails to warn the user.

An example undiagnosed mistake appears in gcc/gcc/java/parse.y near line 1154
                  /* Can't have a static initializer in an innerclass */
                  if ($1 | ACC_STATIC &&
                      ...
The '|' is unlikely to have been intended.

I added a warning for this to "my" gcc years ago, and it works well.  I recently
got this warning added to the Java "findbugs" tool
http://findbugs.sourceforge.net/bugDescriptions.html (That took less than a
week, in stark contrast to my experiences with gcc).

I have a patch, but this web form lacks a way to supply it.

-- 
           Summary: gcc fails to diagnose suspect expressions that have
                    incompatible bit masks
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: trt at acm dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17534