python · mdickinson · Feb 20, 2017 · Feb 20, 2017 · Feb 20, 2017
diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
@@ -8,6 +8,13 @@
 NAN = float("nan")
 # These tests ensure that complex math does the right thing

+# decorator for skipping tests on non-IEEE 754 platforms
+have_getformat = hasattr(float, "__getformat__")
+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 +448,28 @@ 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:
+                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)))

diff --git a/Misc/NEWS b/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.


diff --git a/Objects/complexobject.c b/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);