[Bug c++/57066] New: std::logb(-inf) returns wrong value

[bolero.murakami at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57066

             Bug #: 57066
           Summary: std::logb(-inf) returns wrong value
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: bolero.murak...@gmail.com


auto inf = std::numeric_limits<double>::infinity();
std::cout << std::logb(-inf) << std::endl;

"-inf" is output.
it is wrong.

std::logb(-inf) should returns +inf.
> F.9.3.11 The logb functions
> - logb(±∞) returns +∞.