math.c: fix lgamma

* math.c (ruby_lgamma_r): fix lgamma(-0.0) on mingw and OSX.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54494 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 24 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 802a124bfb..0bb692be56 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,6 @@
-Wed Apr  6 00:52:00 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Wed Apr  6 00:53:31 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* math.c (ruby_lgamma_r): fix lgamma(-0.0) on mingw and OSX.
 
 	* math.c (ruby_tgamma): fix tgamma(-0.0) on mingw.
 	  [ruby-core:74817] [Bug #12249]
diff --git a/math.c b/math.c
index e1dfe975d2..9e97f3a2d2 100644
--- a/math.c
+++ b/math.c
@@ -750,6 +750,22 @@ ruby_tgamma(const double d)
 #define tgamma(d) ruby_tgamma(d)
 #endif
 
+#if defined __MINGW32__ || defined __APPLE__
+static inline double
+ruby_lgamma_r(const double d, int *sign)
+{
+    const double g = lgamma_r(d, sign);
+    if (isinf(g)) {
+	if (d == 0.0 && signbit(d)) {
+	    *sign = -1;
+	    return INFINITY;
+	}
+    }
+    return g;
+}
+#define lgamma_r(d, sign) ruby_lgamma_r(d, sign)
+#endif
+
 /*
  * call-seq:
  *    Math.gamma(x)  -> Float
diff --git a/test/ruby/test_math.rb b/test/ruby/test_math.rb
index c17b21a53d..1d571252ee 100644
--- a/test/ruby/test_math.rb
+++ b/test/ruby/test_math.rb
@@ -275,6 +275,11 @@ class TestMath < Test::Unit::TestCase
     assert_float_and_int([Math.log(6),                1], Math.lgamma(4))
 
     assert_raise(Math::DomainError) { Math.lgamma(-Float::INFINITY) }
+    x, sign = Math.lgamma(-0.0)
+    mesg = "Math.lgamma(-0.0) should be [INF, -1]"
+    assert_infinity(x, mesg)
+    assert_predicate(x, :positive?, mesg)
+    assert_equal(-1, sign, mesg)
   end
 
   def test_fixnum_to_f