lgamma_r.c: fix at -0.0

* math.c (ruby_lgamma_r): missing/lgamma_r.c is used on Windows,
  since msvcrt does not provide it.
* missing/lgamma_r.c (lgamma_r): fix lgamma(-0.0).
  [ruby-core:74823] [Bug #12249]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54496 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 10 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index e9563ddb0d..4a735a6858 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Wed Apr  6 10:17:53 2016  cremno phobia  <cremno@mail.ru>
+
+	* math.c (ruby_lgamma_r): missing/lgamma_r.c is used on Windows,
+	  since msvcrt does not provide it.
+
+	* missing/lgamma_r.c (lgamma_r): fix lgamma(-0.0).
+	  [ruby-core:74823] [Bug #12249]
+
 Wed Apr  6 01:22:55 2016  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* math.c (ruby_lgamma_r): mswin's lgamma_r also seems to be wrong.
diff --git a/math.c b/math.c
index 23c6210373..8c16c76c3b 100644
--- a/math.c
+++ b/math.c
@@ -750,7 +750,7 @@ ruby_tgamma(const double d)
 #define tgamma(d) ruby_tgamma(d)
 #endif
 
-#if defined _WIN32 || defined __APPLE__
+#if defined __APPLE__
 static inline double
 ruby_lgamma_r(const double d, int *sign)
 {
diff --git a/missing/lgamma_r.c b/missing/lgamma_r.c
index 6d2f38f40c..01066d2930 100644
--- a/missing/lgamma_r.c
+++ b/missing/lgamma_r.c
@@ -66,7 +66,7 @@ lgamma_r(double x, int *signp)
         double i, f, s;
         f = modf(-x, &i);
         if (f == 0.0) { /* pole error */
-            *signp = 1;
+            *signp = signbit(x) ? -1 : 1;
             errno = ERANGE;
             return HUGE_VAL;
         }