From: gotoken@... (GOTO Kentaro)
Date: 2001-03-07T17:40:24+09:00
Subject: [ruby-talk:12220] Re: NaN, Infinity (Bug?)

In message "[ruby-talk:12217] Re: NaN, Infinity (Bug?)"
    on 01/03/07, Tammo Freese <tammo.freese@offis.de> writes:
>Perhaps this bug is only based on a misconfiguration of my system?
>I use the windows installer from RubyCentral, version 1.6.2 (-03)
>on Windows NT4. Anybody out there with the same configuration?
>Which results do you get?

This problem is caused by Cygwin's C library libc (newlib). 
The behavior of Cygwin's log() is commented as follows:

  newlib/libm/math/w_log.c:
  >RETURNS
  >Normally, returns the calculated value.  When <[x]> is zero, the
  >returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>.
  >When <[x]> is negative, the returned value is <<-HUGE_VAL>> and
  ><<errno>> is set to <<EDOM>>.  You can control the error behavior via
  ><<matherr>>.

# Based on eban's report [ruby-dev:12385]

For Cygwin, eban added a macro to the current version of Ruby:

#if defined __CYGWIN__
#define log(x) ((x) < 0.0 ? ((x) - (x)) / 0.0 : log(x))
#endif

-- Gotoken