http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51457
Bug #: 51457 Summary: Add warning about impossible boolean comparisons Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: ll...@randombit.net Neither GCC 4.6.0 (release) and 4.7 svn (r181390) warn about the impossible comparison in bool f(bool b) { return (b == 'a'); } The optimizer figures out it is always false and will optimize it to xorl %eax, %eax ret >From the description in the manual I would have expected -Wtype-limits to detect this case.