[Bug c++/60237] New: isnan fails with -ffast-math

[nathanael.schaeffer at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60237

            Bug ID: 60237
           Summary: isnan fails with -ffast-math
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nathanael.schaeffer at gmail dot com

With -ffast-math, isnan should return true if passed a NaN value.
Otherwise, how is isnan different than (x!=x) ?

isnan worked as expected with gcc 4.7, but does not with 4.8.1 and 4.8.2

How can I check if x is a NaN in a portable way (not presuming any compilation
option) ?