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

mdickinson · web-flow · commit 0936a00fe035 · 2017-02-20T21:50:49.000Z
* Fix incorrect handling of signed zeros for complex-related classes. * Add Misc/NEWS entry. (cherry picked from commit 112ec38)
diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
@@ -385,6 +385,29 @@ 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_hash(self):
         for x in range(-30, 30):
             self.assertEqual(hash(x), hash(complex(x, 0)))
diff --git 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
@@ -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);

Original file line number	Diff line number	Diff line change
`@@ -1014,11 +1014,11 @@ complex_new(PyTypeObject type, PyObject args, PyObject *kwds)`
`1014`	`1014`	`return NULL;`
`1015`	`1015`	`}`
`1016`	`1016`	`cr.real = PyFloat_AsDouble(tmp);`
`1017`		`- cr.imag = 0.0; /* Shut up compiler warning */`
	`1017`	`+ cr.imag = 0.0;`
`1018`	`1018`	`Py_DECREF(tmp);`
`1019`	`1019`	`}`
`1020`	`1020`	`if (i == NULL) {`
`1021`		`- ci.real = 0.0;`
	`1021`	`+ ci.real = cr.imag;`
`1022`	`1022`	`}`
`1023`	`1023`	`else if (PyComplex_Check(i)) {`
`1024`	`1024`	`ci = ((PyComplexObject*)i)->cval;`
`@@ -1040,7 +1040,7 @@ complex_new(PyTypeObject type, PyObject args, PyObject *kwds)`
`1040`	`1040`	`if (ci_is_complex) {`
`1041`	`1041`	`cr.real -= ci.imag;`
`1042`	`1042`	`}`
`1043`		`- if (cr_is_complex) {`
	`1043`	`+ if (cr_is_complex && i != NULL) {`
`1044`	`1044`	`ci.real += cr.imag;`
`1045`	`1045`	`}`
`1046`	`1046`	`return complex_subtype_from_doubles(type, cr.real, ci.real);`