fix tgamma for inifity

* configure.in: do not use buggy tgamma() of mingw.

* missing/tgamma.c (tgamma): merge fix for inifity from
  ruby_tgamma.  since msvcr120.dll and later have tgamma, this
  implementation will not be used.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58691 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.in

@@ -1317,6 +1317,7 @@ main()
 		    ac_cv_func___builtin_setjmp=no
 		    ac_cv_func_round=no
 		])
+		ac_cv_func_tgamma=no
 		AC_CHECK_TYPE([NET_LUID], [], [],
 			      [@%:@include <winsock2.h>
 			      @%:@include <iphlpapi.h>])

math.c

@@ -778,22 +778,6 @@ math_erfc(VALUE unused_obj, VALUE x)
     return DBL2NUM(erfc(Get_Double(x)));
 }
 
-#if defined _WIN32
-static inline double
-ruby_tgamma(const double d)
-{
-    const double g = tgamma(d);
-    if (isinf(g)) {
-	if (d == 0.0 && signbit(d)) return -INFINITY;
-    }
-    if (isnan(g)) {
-	if (!signbit(d)) return INFINITY;
-    }
-    return g;
-}
-#define tgamma(d) ruby_tgamma(d)
-#endif
-
 #if defined LGAMMA_R_PM0_FIX
 static inline double
 ruby_lgamma_r(const double d, int *sign)

missing/tgamma.c

@@ -10,9 +10,25 @@ reference - Haruhiko Okumura: C-gengo niyoru saishin algorithm jiten
     gamma.c -- Gamma function
 ***********************************************************/
 #include "ruby/config.h"
+#include "ruby/missing.h"
 #include <math.h>
 #include <errno.h>
 
+#ifdef _WIN32
+# include <float.h>
+# if !defined __MINGW32__ || defined __NO_ISOCEXT
+#  ifndef isnan
+#   define isnan(x) _isnan(x)
+#  endif
+#  ifndef isinf
+#   define isinf(x) (!_finite(x) && !_isnan(x))
+#  endif
+#  ifndef finite
+#   define finite(x) _finite(x)
+#  endif
+# endif
+#endif
+
 #ifndef HAVE_LGAMMA_R
 
 #include <errno.h>
@@ -54,11 +70,16 @@ double tgamma(double x)  /* Gamma function */
         errno = ERANGE;
         return 1/x < 0 ? -HUGE_VAL : HUGE_VAL;
     }
+    if (isinf(x)) {
+        if (x < 0) goto domain_error;
+        return x;
+    }
     if (x < 0) {
         static double zero = 0.0;
         double i, f;
         f = modf(-x, &i);
         if (f == 0.0) { /* Domain Error */
+          domain_error:
             errno = EDOM;
             return zero/zero;
         }