pythongh-102837: improve test coverage for math module (python#102523)

- input checks for math_1(L989), math_1a(L1023), math_2(L1064,L1071), hypot(L2682), log(L2307), ldexp(L2168), ceil(L1165), floor(L1236,L1239) and dist(L2587,L2588,L2628).
- drop inaccessible "if" branch (L3518) in perm_comb_small()
- improve fsum coverage for exceptional cases (L1433,L1438,L1451,L1497), ditto fmod(L2378)
- rewrite modf to fix inaccessible case(L2229), ditto for pow(L2988)
    
(all line numbers are wrt the main branch at 5e6661b)

Author: Sergey B Kirpichev

Lib/test/test_math.py

@@ -235,6 +235,10 @@ def __init__(self, value):
     def __index__(self):
         return self.value
 
+class BadDescr:
+    def __get__(self, obj, objtype=None):
+        raise ValueError
+
 class MathTests(unittest.TestCase):
 
     def ftest(self, name, got, expected, ulp_tol=5, abs_tol=0.0):
@@ -324,6 +328,7 @@ def testAtan2(self):
         self.ftest('atan2(0, 1)', math.atan2(0, 1), 0)
         self.ftest('atan2(1, 1)', math.atan2(1, 1), math.pi/4)
         self.ftest('atan2(1, 0)', math.atan2(1, 0), math.pi/2)
+        self.ftest('atan2(1, -1)', math.atan2(1, -1), 3*math.pi/4)
 
         # math.atan2(0, x)
         self.ftest('atan2(0., -inf)', math.atan2(0., NINF), math.pi)
@@ -417,16 +422,22 @@ def __ceil__(self):
                 return 42
         class TestNoCeil:
             pass
+        class TestBadCeil:
+            __ceil__ = BadDescr()
         self.assertEqual(math.ceil(TestCeil()), 42)
         self.assertEqual(math.ceil(FloatCeil()), 42)
         self.assertEqual(math.ceil(FloatLike(42.5)), 43)
         self.assertRaises(TypeError, math.ceil, TestNoCeil())
+        self.assertRaises(ValueError, math.ceil, TestBadCeil())
 
         t = TestNoCeil()
         t.__ceil__ = lambda *args: args
         self.assertRaises(TypeError, math.ceil, t)
         self.assertRaises(TypeError, math.ceil, t, 0)
 
+        self.assertEqual(math.ceil(FloatLike(+1.0)), +1.0)
+        self.assertEqual(math.ceil(FloatLike(-1.0)), -1.0)
+
     @requires_IEEE_754
     def testCopysign(self):
         self.assertEqual(math.copysign(1, 42), 1.0)
@@ -567,16 +578,22 @@ def __floor__(self):
                 return 42
         class TestNoFloor:
             pass
+        class TestBadFloor:
+            __floor__ = BadDescr()
         self.assertEqual(math.floor(TestFloor()), 42)
         self.assertEqual(math.floor(FloatFloor()), 42)
         self.assertEqual(math.floor(FloatLike(41.9)), 41)
         self.assertRaises(TypeError, math.floor, TestNoFloor())
+        self.assertRaises(ValueError, math.floor, TestBadFloor())
 
         t = TestNoFloor()
         t.__floor__ = lambda *args: args
         self.assertRaises(TypeError, math.floor, t)
         self.assertRaises(TypeError, math.floor, t, 0)
 
+        self.assertEqual(math.floor(FloatLike(+1.0)), +1.0)
+        self.assertEqual(math.floor(FloatLike(-1.0)), -1.0)
+
     def testFmod(self):
         self.assertRaises(TypeError, math.fmod)
         self.ftest('fmod(10, 1)', math.fmod(10, 1), 0.0)
@@ -598,6 +615,7 @@ def testFmod(self):
         self.assertEqual(math.fmod(-3.0, NINF), -3.0)
         self.assertEqual(math.fmod(0.0, 3.0), 0.0)
         self.assertEqual(math.fmod(0.0, NINF), 0.0)
+        self.assertRaises(ValueError, math.fmod, INF, INF)
 
     def testFrexp(self):
         self.assertRaises(TypeError, math.frexp)
@@ -714,6 +732,11 @@ def msum(iterable):
             s = msum(vals)
             self.assertEqual(msum(vals), math.fsum(vals))
 
+        self.assertEqual(math.fsum([1.0, math.inf]), math.inf)
+        self.assertRaises(OverflowError, math.fsum, [1e+308, 1e+308])
+        self.assertRaises(ValueError, math.fsum, [math.inf, -math.inf])
+        self.assertRaises(TypeError, math.fsum, ['spam'])
+
     def testGcd(self):
         gcd = math.gcd
         self.assertEqual(gcd(0, 0), 0)
@@ -831,6 +854,8 @@ def testHypot(self):
             scale = FLOAT_MIN / 2.0 ** exp
             self.assertEqual(math.hypot(4*scale, 3*scale), 5*scale)
 
+        self.assertRaises(TypeError, math.hypot, *([1.0]*18), 'spam')
+
     @requires_IEEE_754
     @unittest.skipIf(HAVE_DOUBLE_ROUNDING,
                      "hypot() loses accuracy on machines with double rounding")
@@ -966,13 +991,19 @@ class T(tuple):
             dist((1, 2, 3, 4), (5, 6, 7))
         with self.assertRaises(ValueError):        # Check dimension agree
             dist((1, 2, 3), (4, 5, 6, 7))
+        with self.assertRaises(TypeError):
+            dist((1,)*17 + ("spam",), (1,)*18)
         with self.assertRaises(TypeError):         # Rejects invalid types
             dist("abc", "xyz")
         int_too_big_for_float = 10 ** (sys.float_info.max_10_exp + 5)
         with self.assertRaises((ValueError, OverflowError)):
             dist((1, int_too_big_for_float), (2, 3))
         with self.assertRaises((ValueError, OverflowError)):
             dist((2, 3), (1, int_too_big_for_float))
+        with self.assertRaises(TypeError):
+            dist((1,), 2)
+        with self.assertRaises(TypeError):
+            dist([1], 2)
 
         # Verify that the one dimensional case is equivalent to abs()
         for i in range(20):
@@ -1111,6 +1142,7 @@ def test_lcm(self):
 
     def testLdexp(self):
         self.assertRaises(TypeError, math.ldexp)
+        self.assertRaises(TypeError, math.ldexp, 2.0, 1.1)
         self.ftest('ldexp(0,1)', math.ldexp(0,1), 0)
         self.ftest('ldexp(1,1)', math.ldexp(1,1), 2)
         self.ftest('ldexp(1,-1)', math.ldexp(1,-1), 0.5)
@@ -1153,6 +1185,7 @@ def testLog(self):
                    2302.5850929940457)
         self.assertRaises(ValueError, math.log, -1.5)
         self.assertRaises(ValueError, math.log, -10**1000)
+        self.assertRaises(ValueError, math.log, 10, -10)
         self.assertRaises(ValueError, math.log, NINF)
         self.assertEqual(math.log(INF), INF)
         self.assertTrue(math.isnan(math.log(NAN)))
@@ -2378,6 +2411,14 @@ def __float__(self):
             # argument to a float.
             self.assertFalse(getattr(y, "converted", False))
 
+    def test_input_exceptions(self):
+        self.assertRaises(TypeError, math.exp, "spam")
+        self.assertRaises(TypeError, math.erf, "spam")
+        self.assertRaises(TypeError, math.atan2, "spam", 1.0)
+        self.assertRaises(TypeError, math.atan2, 1.0, "spam")
+        self.assertRaises(TypeError, math.atan2, 1.0)
+        self.assertRaises(TypeError, math.atan2, 1.0, 2.0, 3.0)
+
     # Custom assertions.
 
     def assertIsNaN(self, value):

Modules/mathmodule.c

@@ -2195,12 +2195,10 @@ math_modf_impl(PyObject *module, double x)
     double y;
     /* some platforms don't do the right thing for NaNs and
        infinities, so we take care of special cases directly. */
-    if (!Py_IS_FINITE(x)) {
-        if (Py_IS_INFINITY(x))
-            return Py_BuildValue("(dd)", copysign(0., x), x);
-        else if (Py_IS_NAN(x))
-            return Py_BuildValue("(dd)", x, x);
-    }
+    if (Py_IS_INFINITY(x))
+        return Py_BuildValue("(dd)", copysign(0., x), x);
+    else if (Py_IS_NAN(x))
+        return Py_BuildValue("(dd)", x, x);
 
     errno = 0;
     x = modf(x, &y);
@@ -2950,7 +2948,8 @@ math_pow_impl(PyObject *module, double x, double y)
             else /* y < 0. */
                 r = odd_y ? copysign(0., x) : 0.;
         }
-        else if (Py_IS_INFINITY(y)) {
+        else {
+            assert(Py_IS_INFINITY(y));
             if (fabs(x) == 1.0)
                 r = 1.;
             else if (y > 0. && fabs(x) > 1.0)
@@ -3480,9 +3479,7 @@ static const uint8_t factorial_trailing_zeros[] = {
 static PyObject *
 perm_comb_small(unsigned long long n, unsigned long long k, int iscomb)
 {
-    if (k == 0) {
-        return PyLong_FromLong(1);
-    }
+    assert(k != 0);
 
     /* For small enough n and k the result fits in the 64-bit range and can
      * be calculated without allocating intermediate PyLong objects. */