bpo-29602: fix signed zero handling in complex constructor

Author: mdickinson

Lib/test/test_complex.py

@@ -8,6 +8,12 @@
 NAN = float("nan")
 # These tests ensure that complex math does the right thing
 
+# decorator for skipping tests on non-IEEE 754 platforms
+requires_IEEE_754 = unittest.skipUnless(have_getformat and
+ float.__getformat__("double").startswith("IEEE"),
+ "test requires IEEE 754 doubles")
+
+
 class ComplexTest(unittest.TestCase):
 
  def assertAlmostEqual(self, a, b):
@@ -441,6 +447,29 @@ def __rmod__(self,other):
  b = 'y %s x' % op
  self.assertTrue(type(eval(a)) is type(eval(b)) is xcomplex)
 
+ @requires_IEEE_754
+ def test_constructor_special_numbers(self):
+ class complex2(complex):
+ pass
+ for x in 0.0, -0.0, INF, -INF, NAN:
+ for y in 0.0, -0.0, INF, -INF, NAN:
+ with self.subTest(x=x, y=y):
+ z = complex(x, y)
+ self.assertFloatsAreIdentical(z.real, x)
+ self.assertFloatsAreIdentical(z.imag, y)
+ z = complex2(x, y)
+ self.assertIs(type(z), complex2)
+ self.assertFloatsAreIdentical(z.real, x)
+ self.assertFloatsAreIdentical(z.imag, y)
+ z = complex(complex2(x, y))
+ self.assertIs(type(z), complex)
+ self.assertFloatsAreIdentical(z.real, x)
+ self.assertFloatsAreIdentical(z.imag, y)
+ z = complex2(complex(x, y))
+ self.assertIs(type(z), complex2)
+ self.assertFloatsAreIdentical(z.real, x)
+ self.assertFloatsAreIdentical(z.imag, y)
+
  def test_hash(self):
  for x in xrange(-30, 30):
  self.assertEqual(hash(x), hash(complex(x, 0)))

Misc/NEWS

@@ -10,6 +10,10 @@ What's New in Python 2.7.14?
 Core and Builtins
 -----------------
 
+- bpo-29602: Fix incorrect handling of signed zeros in complex constructor for
+ complex subclasses and for inputs having a __complex__ method. Patch
+ by Serhiy Storchaka.
+
 - bpo-29347: Fixed possibly dereferencing undefined pointers
  when creating weakref objects.
 

Objects/complexobject.c

@@ -1232,11 +1232,11 @@ complex_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
  return NULL;
  }
  cr.real = PyFloat_AsDouble(tmp);
- cr.imag = 0.0; /* Shut up compiler warning */
+ cr.imag = 0.0;
  Py_DECREF(tmp);
  }
  if (i == NULL) {
- ci.real = 0.0;
+ ci.real = cr.imag;
  }
  else if (PyComplex_Check(i)) {
  ci = ((PyComplexObject*)i)->cval;
@@ -1258,7 +1258,7 @@ complex_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
  if (ci_is_complex) {
  cr.real -= ci.imag;
  }
- if (cr_is_complex) {
+ if (cr_is_complex && i != NULL) {
  ci.real += cr.imag;
  }
  return complex_subtype_from_doubles(type, cr.real, ci.real);