gh-102837: few coverage nitpicks for the math module

- input checks for math_1(L989), math_1a(L1023), math_2(L1064,L1071),
  hypot(L2682), log(L2307), ldexp(L2168) and dist(L2587,L2588,L2628).
- rewrite math_floor like math_ceil (cover L1239)
- 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 wrt the main branch at 5e6661b)

Lib/test/test_math.py

@@ -324,6 +324,7 @@ 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)
@@ -598,6 +599,7 @@ 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 +716,11 @@ 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 +838,8 @@ 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 +975,19 @@ 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 +1126,7 @@ 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 +1169,7 @@ 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)))
@@ -2364,6 +2381,14 @@ 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

@@ -1219,13 +1219,7 @@ static PyObject *
 math_floor(PyObject *module, PyObject *number)
 /*[clinic end generated code: output=c6a65c4884884b8a input=63af6b5d7ebcc3d6]*/
 {
-    double x;
-
-    if (PyFloat_CheckExact(number)) {
-        x = PyFloat_AS_DOUBLE(number);
-    }
-    else
-    {
+    if (!PyFloat_CheckExact(number)) {
         math_module_state *state = get_math_module_state(module);
         PyObject *method = _PyObject_LookupSpecial(number, state->str___floor__);
         if (method != NULL) {
@@ -1235,10 +1229,11 @@ math_floor(PyObject *module, PyObject *number)
         }
         if (PyErr_Occurred())
             return NULL;
-        x = PyFloat_AsDouble(number);
-        if (x == -1.0 && PyErr_Occurred())
-            return NULL;
     }
+    double x = PyFloat_AsDouble(number);
+    if (x == -1.0 && PyErr_Occurred())
+        return NULL;
+
     return PyLong_FromDouble(floor(x));
 }
 
@@ -2223,12 +2218,10 @@ 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);
@@ -2985,7 +2978,7 @@ 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 { /* Py_IS_INFINITY(y) */
             if (fabs(x) == 1.0)
                 r = 1.;
             else if (y > 0. && fabs(x) > 1.0)
@@ -3515,10 +3508,6 @@ 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);
-    }
-
     /* For small enough n and k the result fits in the 64-bit range and can
      * be calculated without allocating intermediate PyLong objects. */
     if (iscomb) {