commit 441b8e6fe7b995e6cd29d33c7ea7f37b87d60d3b
Author: Marc-Andre Lafortune <github@marc-andre.ca>
Date:   Fri Feb 17 19:10:21 2012 -0500

    * numeric.c (flodivmod): Fix for cornercases [Bug #xxxx]
    
    * insns.def (opt_mod): Bring up to date with flodivmod
    
    * test/ruby/test_float.rb: tests for above
    
    * test/ruby/envutil.rb: create helper assert_is_minus_zero

diff --git a/insns.def b/insns.def
index 59a98c0..dbde0bc 100644
--- a/insns.def
+++ b/insns.def
@@ -1620,19 +1620,21 @@ opt_mod
 		 BASIC_OP_UNREDEFINED_P(BOP_MOD, FLOAT_REDEFINED_OP_FLAG)) {
 	    double x = RFLOAT_VALUE(recv);
 	    double y = RFLOAT_VALUE(obj);
-	    double div, mod;
-
-	    {
+	    double mod;
+#ifdef HAVE_FMOD
+	    mod = fmod(x, y);
+#else
+	    if((x == -0.0) || (isinf(y) && !isinf(x)))
+	        mod = x;
+	    else {
 		double z;
 
-		modf(x / y, &z);
+		modf(x/y, &z);
 		mod = x - z * y;
 	    }
-
-	    div = (x - mod) / y;
+#endif
 	    if (y * mod < 0) {
 		mod += y;
-		div -= 1.0;
 	    }
 	    val = DBL2NUM(mod);
 	}
diff --git a/numeric.c b/numeric.c
index 3b09fea..6a4518d 100644
--- a/numeric.c
+++ b/numeric.c
@@ -811,19 +811,27 @@ flo_quo(VALUE x, VALUE y)
 static void
 flodivmod(double x, double y, double *divp, double *modp)
 {
+    /******
+    Modifications to this implementation should be mirrored in insns.def
+    *******/
+
     double div, mod;
 
     if (y == 0.0) rb_num_zerodiv();
+
 #ifdef HAVE_FMOD
     mod = fmod(x, y);
 #else
-    {
+    if((x == -0.0) || (isinf(y) && !isinf(x)))
+        mod = x;
+    else {
 	double z;
 
 	modf(x/y, &z);
 	mod = x - z * y;
     }
 #endif
+
     if (isinf(x) && !isinf(y) && !isnan(y))
 	div = x;
     else
diff --git a/test/ruby/envutil.rb b/test/ruby/envutil.rb
index 69b037b..0f9c453 100644
--- a/test/ruby/envutil.rb
+++ b/test/ruby/envutil.rb
@@ -206,6 +206,10 @@ module Test
         assert_equal([true, ""], [status.success?, err], message)
         assert_operator(after.fdiv(before), :<, limit, message)
       end
+
+      def assert_is_minus_zero(f)
+        assert(1.0/f == -Float::INFINITY, "#{f} is not -0.0")
+      end
     end
   end
 end
diff --git a/test/ruby/test_float.rb b/test/ruby/test_float.rb
index 1935cfd..ba94cb0 100644
--- a/test/ruby/test_float.rb
+++ b/test/ruby/test_float.rb
@@ -195,6 +195,13 @@ class TestFloat < Test::Unit::TestCase
     assert_raise(TypeError) { 2.0.send(:%, nil) }
   end
 
+  def test_modulo3
+    assert_equal(4.2, 4.2.send(:%, Float::INFINITY))
+    assert_equal(4.2, 4.2 % Float::INFINITY)
+    assert_is_minus_zero(-0.0 % 4.2)
+    assert_is_minus_zero(-0.0.send :%, 4.2)
+  end
+
   def test_divmod2
     assert_equal([1.0, 0.0], 2.0.divmod(2))
     assert_equal([1.0, 0.0], 2.0.divmod((2**32).coerce(2).first))