Warn about creating global variables by __setattr__ that shadow builtin
names. Unfortunately, this is not bulletproof since the module
dictionary can be modified directly.
diff --git a/Misc/NEWS b/Misc/NEWS
index 6c9f5e5..35b35b8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -43,6 +43,12 @@
instead of going through __getitem__. If __getitem__ access is
preferred, then __iter__ can be overriden.
+- Creating an attribute on a module (i.e. a global variable created by
+ __setattr__) that causes a builtin name to be shadowed now raises a
+ DeprecationWarning. In future versions of Python the effect may be
+ undefined (in order to allow for optimization of global and builtin
+ name lookups).
+
Extension modules
-----------------
diff --git a/Objects/moduleobject.c b/Objects/moduleobject.c
index 812cbc4..5195388 100644
--- a/Objects/moduleobject.c
+++ b/Objects/moduleobject.c
@@ -198,6 +198,71 @@
return PyString_FromFormat("<module '%s' from '%s'>", name, filename);
}
+static PyObject *
+find_builtin_names(void)
+{
+ PyObject *builtins, *names, *key, *value;
+ int pos = 0;
+ builtins = PyEval_GetBuiltins();
+ if (builtins == NULL || !PyDict_Check(builtins)) {
+ PyErr_SetString(PyExc_SystemError, "no builtins dict!");
+ return NULL;
+ }
+ names = PyDict_New();
+ if (names == NULL)
+ return NULL;
+ while (PyDict_Next(builtins, &pos, &key, &value)) {
+ if (PyString_Check(key) &&
+ PyString_Size(key) > 0 &&
+ PyString_AS_STRING(key)[0] != '_') {
+ if (PyDict_SetItem(names, key, Py_None) < 0) {
+ Py_DECREF(names);
+ return NULL;
+ }
+ }
+ }
+ return names;
+}
+
+/* returns 0 or 1 (and -1 on error) */
+static int
+shadows_builtin(PyObject *globals, PyObject *name)
+{
+ static PyObject *builtin_names = NULL;
+ if (builtin_names == NULL) {
+ builtin_names = find_builtin_names();
+ if (builtin_names == NULL)
+ return -1;
+ }
+ if (!PyString_Check(name))
+ return 0;
+ if (PyDict_GetItem(globals, name) == NULL &&
+ PyDict_GetItem(builtin_names, name) != NULL) {
+ return 1;
+ }
+ else {
+ return 0;
+ }
+}
+
+static int
+module_setattr(PyObject *m, PyObject *name, PyObject *value)
+{
+ PyObject *globals = ((PyModuleObject *)m)->md_dict;
+ PyObject *builtins = PyEval_GetBuiltins();
+ if (globals != NULL && globals != builtins) {
+ int shadows = shadows_builtin(globals, name);
+ if (shadows == 1) {
+ if (PyErr_Warn(PyExc_DeprecationWarning,
+ "assignment shadows builtin") < 0)
+ return -1;
+ }
+ else if (shadows == -1)
+ return -1;
+ }
+ return PyObject_GenericSetAttr(m, name, value);
+}
+
/* We only need a traverse function, no clear function: If the module
is in a cycle, md_dict will be cleared as well, which will break
the cycle. */
@@ -234,7 +299,7 @@
0, /* tp_call */
0, /* tp_str */
PyObject_GenericGetAttr, /* tp_getattro */
- PyObject_GenericSetAttr, /* tp_setattro */
+ module_setattr, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
Py_TPFLAGS_BASETYPE, /* tp_flags */