[cfe-dev] signbit returns false for negative NaN

[victor.zverovich at gmail.com]

Hello,

When compiling with a recent version of Clang, the following code

  std::signbit(-std::numeric_limits<double>::quiet_NaN())

returns true with optimizations disabled and false with
optimizations enabled. Other compilers like GCC and older versions of Clang
always return true as expected. Is it a bug or a feature?

I'm using Apple LLVM version 5.1 (clang-503.0.38) (based on LLVM 3.4svn).

Thanks,
Victor
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