configure.in: check atan2

* configure.in (rb_cv_atan2_inf_c99): check whether runtime atan2
  handles Inf as C99.  ruby-core:62536] [Bug #9831]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45930 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Mon May 12 23:57:15 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* configure.in (rb_cv_atan2_inf_c99): check whether runtime atan2
+	  handles Inf as C99.  ruby-core:62536] [Bug #9831]
+
 Mon May 12 20:33:01 2014  Tanaka Akira  <akr@fsij.org>
 
 	* configure.in: Invoke AC_REPLACE_FUNCS for each function.

configure.in

@@ -2145,6 +2145,35 @@ void qsort_r(void *base, size_t nmemb, size_t size,
   ])
 fi
 
+AC_CACHE_CHECK(whether atan2 handles Inf as C99, rb_cv_atan2_inf_c99, [
+    AS_IF([test $ac_cv_func_atan2f:$ac_cv_func_atan2l = yes:yes], [
+	AC_TRY_RUN([
+@%:@include <math.h>
+@%:@ifdef HAVE_UNISTD_H
+@%:@include <unistd.h>
+@%:@endif
+@%:@ifndef EXIT_SUCCESS
+@%:@define EXIT_SUCCESS 0
+@%:@endif
+@%:@ifndef EXIT_FAILURE
+@%:@define EXIT_FAILURE 1
+@%:@endif
+
+int
+main(int argc, char **argv)
+{
+    if (fabs(atan2(INFINITY, INFINITY) - M_PI_4) <= 0.01) return EXIT_SUCCESS;
+    return EXIT_FAILURE;
+}
+],
+	[rb_cv_atan2_inf_c99=yes],
+	[rb_cv_atan2_inf_c99=no],
+	[AS_CASE($target_os, [mingw*|mswin*], [rb_cv_atan2_inf_c99=no], [rb_cv_atan2_inf_c99=yes])]
+	)
+    ])
+])
+AS_IF([test $rb_cv_atan2_inf_c99 = yes], [AC_DEFINE(ATAN2_INF_C99)])
+
 # Some platform need -lrt for clock_gettime, but the other don't.
 if test x"$ac_cv_func_clock_gettime" != xyes; then
     # glibc 2.17 moves clock_* functions from librt to the main C library.

math.c

@@ -79,8 +79,7 @@ math_atan2(VALUE obj, VALUE y, VALUE x)
 	    return DBL2NUM(M_PI);
 	return DBL2NUM(-M_PI);
     }
-#if !(defined(HAVE_ATAN2L) && defined(HAVE_ATAN2F))
-    /* assume atan2() doesn't handle Inf as C99 */
+#ifndef ATAN2_INF_C99
     if (isinf(dx) && isinf(dy)) {
 	/* optimization for FLONUM */
 	if (dx < 0.0) {