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

1 files changed, 16 insertions, 0 deletions

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