[Bug middle-end/44420] New: [feature request] Warn for certain integer overflows

[fm3 at os dot inf dot tu-dresden dot de]

This is a follow-up to http://gcc.gnu.org/ml/gcc-help/2010-06/msg00005.html :

Consider the following case:

  uint32_t foo, bar;
  ...
  foo = bar << 20;

Of course, this operation can overflow and warning about this probably does not
make sense as the programmer should be aware of this case. However, a warning
in the following case could be appropriate IMO:

  uint32_t bar;
  uint64_t foo;
  ...
  foo = bar << 20;

The intension is to catch the overflow case, therefore the assignment to a
64-bit variable. The intended code would be

  uint32_t bar;
  uint64_t foo;
  ...
  foo = (uint64_t)bar << 20;

I think it would be a big help if gcc could warn in the 2nd case.


-- 
           Summary: [feature request] Warn for certain integer overflows
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: fm3 at os dot inf dot tu-dresden dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44420