Issue 2440: remove the guard around the handling of case 'n' in getargs.c's…

Issue 2440: remove the guard around the handling of case 'n' in getargs.c's convertsimple() such that we always treat it as an index type, regardless of whether or not sizeof(size_t) == sizeof(long).  Fix the test_args2.Signed_TestCase.test_n() such that it tests for adherence to PEP 357 (don't try and coerce objects that don't have nb_index slots but do have nb_int slots (i.e. floats) into indexes 'just because we can').  Three other commits are related to this one: r62269 and r62279, which were changes to PyNumber_Index (among other things) to check for nb_int slots when we lack nb_index slots -- and r62292, which is when I reverted these changes after various people pointed out that the test was in fact wrong, not the code.

Lib/test/test_getargs2.py

@@ -187,8 +187,8 @@ class Signed_TestCase(unittest.TestCase):
         # n returns 'Py_ssize_t', and does range checking
         # (PY_SSIZE_T_MIN ... PY_SSIZE_T_MAX)
         self.assertRaises(TypeError, getargs_n, 3.14)
-        self.failUnlessEqual(99, getargs_n(Long()))
-        self.failUnlessEqual(99, getargs_n(Int()))
+        self.assertRaises(TypeError, getargs_n, Long())
+        self.assertRaises(TypeError, getargs_n, Int())
 
         self.assertRaises(OverflowError, getargs_n, PY_SSIZE_T_MIN-1)
         self.failUnlessEqual(PY_SSIZE_T_MIN, getargs_n(PY_SSIZE_T_MIN))

Python/getargs.c

@@ -663,7 +663,6 @@ convertsimple(PyObject *arg, const char **p_format, va_list *p_va, int flags,
 	}
 
 	case 'n': /* Py_ssize_t */
-#if SIZEOF_SIZE_T != SIZEOF_LONG
 	{
 		PyObject *iobj;
 		Py_ssize_t *p = va_arg(*p_va, Py_ssize_t *);
@@ -672,14 +671,12 @@ convertsimple(PyObject *arg, const char **p_format, va_list *p_va, int flags,
 			return converterr("integer<n>", arg, msgbuf, bufsize);
 		iobj = PyNumber_Index(arg);
 		if (iobj != NULL)
-			ival = PyLong_AsSsize_t(arg);
+			ival = PyLong_AsSsize_t(iobj);
 		if (ival == -1 && PyErr_Occurred())
 			return converterr("integer<n>", arg, msgbuf, bufsize);
 		*p = ival;
 		break;
 	}
-#endif
-	/* Fall through from 'n' to 'l' if Py_ssize_t is int */
 	case 'l': {/* long int */
 		long *p = va_arg(*p_va, long *);
 		long ival;