* configure.in (rb_cv_lgamma_r_pm0): check if lgamma_r(+0.0)

  returns positive infinity, in addition to lgamma_r(-0.0).
  AIX returns an incorrect result of negative infinity.

* math.c (ruby_lgamma_r): handle +0.0, in addition to -0.0.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54803 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 24 insertions, 7 deletions

diff --git a/ChangeLog b/ChangeLog
index e91aaf7684..5cf25f9217 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Thu Apr 28 04:49:07 2016  Rei Odaira  <Rei.Odaira@gmail.com>
+
+	* configure.in (rb_cv_lgamma_r_pm0): check if lgamma_r(+0.0)
+	  returns positive infinity, in addition to lgamma_r(-0.0).
+	  AIX returns an incorrect result of negative infinity.
+
+	* math.c (ruby_lgamma_r): handle +0.0, in addition to -0.0.
+
 Thu Apr 28 01:11:14 2016  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* time.c: define _DEFAULT_SOURCE because glibc 2.20 depracates
diff --git a/configure.in b/configure.in
index 292e40ce1a..1042b0329c 100644
--- a/configure.in
+++ b/configure.in
@@ -2503,7 +2503,7 @@ main(int argc, char **argv)
 AS_IF([test "x$rb_cv_atan2_inf_c99" = xyes], [AC_DEFINE(ATAN2_INF_C99)])
 
 AS_IF([test "x$ac_cv_func_lgamma_r" = xyes], [
-    AC_CACHE_CHECK(whether lgamma_r handles -0.0, rb_cv_lgamma_r_m0, [
+    AC_CACHE_CHECK(whether lgamma_r handles +0.0 and -0.0, rb_cv_lgamma_r_pm0, [
 	AC_TRY_RUN([
 @%:@include <math.h>
 @%:@ifdef HAVE_UNISTD_H
@@ -2519,22 +2519,28 @@ AS_IF([test "x$ac_cv_func_lgamma_r" = xyes], [
 int
 main(int argc, char **argv)
 {
-    int sign;
+    int sign = 0;
     double x = lgamma_r(-0.0, &sign);
 
     /* should be [+inf, -1] */
     if (x <= 0) return EXIT_FAILURE;
     if (!isinf(x)) return EXIT_FAILURE;
     if (sign != -1) return EXIT_FAILURE;
+
+    /* should be [+inf, 1] */
+    x = lgamma_r(+0.0, &sign);
+    if (x <= 0) return EXIT_FAILURE;
+    if (!isinf(x)) return EXIT_FAILURE;
+    if (sign != 1) return EXIT_FAILURE;
     return EXIT_SUCCESS;
 }
 ],
-	[rb_cv_lgamma_r_m0=yes],
-	[rb_cv_lgamma_r_m0=no],
-	[rb_cv_lgamma_r_m0=yes]
+	[rb_cv_lgamma_r_pm0=yes],
+	[rb_cv_lgamma_r_pm0=no],
+	[rb_cv_lgamma_r_pm0=yes]
 	)
     ])
-    AS_IF([test "x$rb_cv_lgamma_r_m0" = xno], [AC_DEFINE(LGAMMA_R_M0_FIX)])
+    AS_IF([test "x$rb_cv_lgamma_r_pm0" = xno], [AC_DEFINE(LGAMMA_R_PM0_FIX)])
 ])
 
 # Some platform need -lrt for clock_gettime, but the other don't.
diff --git a/math.c b/math.c
index 9ac898f0ba..c3fe7dbd09 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 LGAMMA_R_M0_FIX
+#if defined LGAMMA_R_PM0_FIX
 static inline double
 ruby_lgamma_r(const double d, int *sign)
 {
@@ -759,6 +759,9 @@ ruby_lgamma_r(const double d, int *sign)
 	if (d == 0.0 && signbit(d)) {
 	    *sign = -1;
 	    return INFINITY;
+	} else if (d == 0.0 && !signbit(d)) {
+	    *sign = 1;
+	    return INFINITY;
 	}
     }
     return g;