bpo-29602: fix signed zero handling in complex constructor. (#203) (#205)

* Fix incorrect handling of signed zeros for complex-related classes.

* Add Misc/NEWS entry.

(cherry picked from commit 112ec38c15b388fe025ccb85369a584d218b1160)

diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
index 403ee3bc580f0a4d122b47fe7f058ca5081b860c..8d551a4fc54c0577c2e3349330e1e1d252c2a7bb 100644 (file)
--- a/Lib/test/test_complex.py
+++ b/Lib/test/test_complex.py
@@ -385,6 +385,29 @@ class ComplexTest(unittest.TestCase):
         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_hash(self):
         for x in range(-30, 30):
             self.assertEqual(hash(x), hash(complex(x, 0)))

diff --git a/Misc/NEWS b/Misc/NEWS
index 52c87d88c72664f3bd7f1bab9f093ccadc790597..038233735f6c1351b1d9db08019813db257fe496 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,10 @@ Release date: XXXX-XX-XX
 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
index d82c5eb9f1ea44e01a79381ef279bae69d7d6cf2..606c1011f4d5c29db0f7c05ac9b3fe1461433819 100644 (file)
--- a/Objects/complexobject.c
+++ b/Objects/complexobject.c
@@ -1014,11 +1014,11 @@ 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;
@@ -1040,7 +1040,7 @@ 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);