[Bug c/21664] New: array-of-empty-structure extension not properly defined

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

For

struct {} a[4]; int main() { return &a[2] - &a[1]; }

the C frontend emits

  return 0 /[ex] 0;

which will, at -O0 fault at runtime, at -O not due to RTL CSE.

Is this even well-defined?  Should the C-frontend rather emit

 return 0;

?  Of course this contradicts the C standard, but that does not
allow empty structures anyway.

-- 
           Summary: array-of-empty-structure extension not properly defined
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21664