Re: [Boost-bugs] [Boost C++ Libraries] #9748: cyl_bessel_j returns incorrect sign when using --fast-math on GCC or -std=c++11 on Intel Compiler

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #9748: cyl_bessel_j returns incorrect sign when using --fast-math on GCC or -std=c++11 on Intel Compiler
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-03-09 18:40:46

#9748: cyl_bessel_j returns incorrect sign when using --fast-math on GCC or
-std=c++11 on Intel Compiler
----------------------------------------+-------------------------
  Reporter:  Dustin Lanham <lanhamd@…>  |      Owner:  johnmaddock
      Type:  Bugs                       |     Status:  new
 Milestone:  To Be Determined           |  Component:  math
   Version:  Boost 1.55.0               |   Severity:  Problem
Resolution:                             |   Keywords:
----------------------------------------+-------------------------

Comment (by johnmaddock):

 To a degree, this is not our bug, a reduced test case is simply:

 {{{
    long double ld = -5.3165867831218916301793863361917824e-2467L;
    std::cout << std::signbit(ld) << std::endl;
 }}}

 Which incorrectly outputs 0 when compiling with --fast-math.

 I suspect there may be other std lib functions which have similar issues
 too, I'll investigate working around this one, but you may just get
 whacked by another...

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/9748#comment:3>
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