From 20362a820bd09617a33721191aa966416b03427c Mon Sep 17 00:00:00 2001
From: Alex Martelli <aleaxit@gmail.com>
Date: Wed, 23 Aug 2006 20:42:02 +0000
Subject: x**2 should about equal x*x (including for a float x such that the
 result is inf) but didn't; added a test to test_float to verify that, and
 ignored the ERANGE value for errno in the pow operation to make the new test
 pass (with help from Marilyn Davis at the Google Python Sprint -- thanks!).

---
 Lib/test/test_float.py | 15 ++++++++++++++-
 Objects/floatobject.c  |  6 +++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py
index fb47db8..d616ad9 100644
--- a/Lib/test/test_float.py
+++ b/Lib/test/test_float.py
@@ -99,12 +99,25 @@ class IEEEFormatTestCase(unittest.TestCase):
                               ('<f', LE_FLOAT_NAN)]:
                 struct.unpack(fmt, data)
 
+# on an IEEE platform, "overflowing" operations produce infinity
+
+class IEEEOperationsTestCase(unittest.TestCase):
+    if float.__getformat__("double").startswith("IEEE"):
+        def test_double_infinity(self):
+            big = 4.8e159
+            pro = big*big
+            self.assertEquals(repr(pro), 'inf')
+            sqr = big**2
+            self.assertEquals(repr(sqr), 'inf')
+
 
 def test_main():
     test_support.run_unittest(
         FormatFunctionsTestCase,
         UnknownFormatTestCase,
-        IEEEFormatTestCase)
+        IEEEFormatTestCase,
+        IEEEOperationsTestCase,
+        )
 
 if __name__ == '__main__':
     test_main()
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index fa09084..5aeabd9 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -821,12 +821,12 @@ float_pow(PyObject *v, PyObject *w, PyObject *z)
 	ix = pow(iv, iw);
 	PyFPE_END_PROTECT(ix)
 	Py_ADJUST_ERANGE1(ix);
-	if (errno != 0) {
+        /* we need to ignore ERANGE here and just return inf */
+	if (errno != 0 && errno != ERANGE) {
 		/* We don't expect any errno value other than ERANGE, but
 		 * the range of libm bugs appears unbounded.
 		 */
-		PyErr_SetFromErrno(errno == ERANGE ? PyExc_OverflowError :
-						     PyExc_ValueError);
+		PyErr_SetFromErrno(PyExc_ValueError);
 		return NULL;
 	}
 	return PyFloat_FromDouble(ix);
-- 
cgit v0.12