[Python-checkins] cpython: Issue #20539: Improve math.factorial error messages and types for large inputs.

[mark.dickinson]

http://hg.python.org/cpython/rev/273e17260d25
changeset:   90218:273e17260d25
user:        Mark Dickinson <dickinsm at gmail.com>
date:        Thu Apr 10 09:29:39 2014 -0400
summary:
  Issue #20539: Improve math.factorial error messages and types for large inputs.
- Better message for the OverflowError in large positive inputs.
- Changed exception type from OverflowError to ValueError for large negative inputs.

files:
  Lib/test/test_math.py |  12 ++++++++++--
  Misc/NEWS             |   4 ++++
  Modules/mathmodule.c  |  16 ++++++++++++----
  3 files changed, 26 insertions(+), 6 deletions(-)


diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -422,9 +422,17 @@
             self.assertEqual(math.factorial(i), py_factorial(i))
         self.assertRaises(ValueError, math.factorial, -1)
         self.assertRaises(ValueError, math.factorial, -1.0)
+        self.assertRaises(ValueError, math.factorial, -10**100)
+        self.assertRaises(ValueError, math.factorial, -1e100)
         self.assertRaises(ValueError, math.factorial, math.pi)
-        self.assertRaises(OverflowError, math.factorial, sys.maxsize+1)
-        self.assertRaises(OverflowError, math.factorial, 10e100)
+
+    # Other implementations may place different upper bounds.
+    @support.cpython_only
+    def testFactorialHugeInputs(self):
+        # Currently raises ValueError for inputs that are too large
+        # to fit into a C long.
+        self.assertRaises(OverflowError, math.factorial, 10**100)
+        self.assertRaises(OverflowError, math.factorial, 1e100)
 
     def testFloor(self):
         self.assertRaises(TypeError, math.floor)
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -31,6 +31,10 @@
 Library
 -------
 
+- Issue #20539: Improved math.factorial error message for large positive inputs
+  and changed exception type (OverflowError -> ValueError) for large negative
+  inputs.
+
 - Issue #21172: isinstance check relaxed from dict to collections.Mapping.
 
 - Issue #21155: asyncio.EventLoop.create_unix_server() now raises a ValueError
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -1408,6 +1408,7 @@
 math_factorial(PyObject *self, PyObject *arg)
 {
     long x;
+    int overflow;
     PyObject *result, *odd_part, *two_valuation;
 
     if (PyFloat_Check(arg)) {
@@ -1421,15 +1422,22 @@
         lx = PyLong_FromDouble(dx);
         if (lx == NULL)
             return NULL;
-        x = PyLong_AsLong(lx);
+        x = PyLong_AsLongAndOverflow(lx, &overflow);
         Py_DECREF(lx);
     }
     else
-        x = PyLong_AsLong(arg);
+        x = PyLong_AsLongAndOverflow(arg, &overflow);
 
-    if (x == -1 && PyErr_Occurred())
+    if (x == -1 && PyErr_Occurred()) {
         return NULL;
-    if (x < 0) {
+    }
+    else if (overflow == 1) {
+        PyErr_Format(PyExc_OverflowError,
+                     "factorial() argument should not exceed %ld",
+                     LONG_MAX);
+        return NULL;
+    }
+    else if (overflow == -1 || x < 0) {
         PyErr_SetString(PyExc_ValueError,
                         "factorial() not defined for negative values");
         return NULL;

-- 
Repository URL: http://hg.python.org/cpython