python · mdickinson · Feb 20, 2017 · Feb 20, 2017
diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
@@ -387,6 +387,29 @@ def __complex__(self):
        self.assertAlmostEqual(complex(complex1(1j)), 2j)
        self.assertRaises(TypeError, complex, complex2(1j))

+    @support.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_underscores(self):
        # check underscores
        for lit in VALID_UNDERSCORE_LITERALS:

diff --git a/Misc/NEWS b/Misc/NEWS
@@ -10,6 +10,10 @@ What's New in Python 3.6.1 release candidate 1?
 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
@@ -1025,11 +1025,11 @@ 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;
@@ -1051,7 +1051,7 @@ 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);