[Bug c++/45918] New: Lack of warning on meaningless unsigned to zero comparison

[yuri at tsoft dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45918

           Summary: Lack of warning on meaningless unsigned to zero
                    comparison
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: y...@tsoft.com


In this case idx<NUM-1 is always false.
gcc should issue an error: comparison is always false due to the value range
limitations.

--- testcase ---
typedef unsigned size_t;

template<size_t NUM>
struct G {
  void fn();
};

template<size_t NUM>
void G<NUM>::fn() {
    for (size_t idx = 0; idx<NUM-1; idx++) {
    }
}

template struct G<1>;