Do not copy free variables to locals in class namespaces.
Fixes bug 1569356, but at the cost of a minor incompatibility in
locals(). Add test that verifies that the class namespace is not
polluted. Also clarify the behavior in the library docs.
Along the way, cleaned up the dict_to_map and map_to_dict
implementations and added some comments that explain what they do.
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 3a073b6..642d77c 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -701,18 +701,38 @@
return b;
}
-/* Convert between "fast" version of locals and dictionary version */
+/* Convert between "fast" version of locals and dictionary version.
+
+ map and values are input arguments. map is a tuple of strings.
+ values is an array of PyObject*. At index i, map[i] is the name of
+ the variable with value values[i]. The function copies the first
+ nmap variable from map/values into dict. If values[i] is NULL,
+ the variable is deleted from dict.
+
+ If deref is true, then the values being copied are cell variables
+ and the value is extracted from the cell variable before being put
+ in dict.
+
+ Exceptions raised while modifying the dict are silently ignored,
+ because there is no good way to report them.
+ */
static void
map_to_dict(PyObject *map, Py_ssize_t nmap, PyObject *dict, PyObject **values,
- Py_ssize_t deref)
+ int deref)
{
Py_ssize_t j;
+ assert(PyTuple_Check(map));
+ assert(PyDict_Check(dict));
+ assert(PyTuple_Size(map) > nmap);
for (j = nmap; --j >= 0; ) {
PyObject *key = PyTuple_GET_ITEM(map, j);
PyObject *value = values[j];
- if (deref)
+ assert(PyString_Check(key));
+ if (deref) {
+ assert(PyCell_Check(value));
value = PyCell_GET(value);
+ }
if (value == NULL) {
if (PyObject_DelItem(dict, key) != 0)
PyErr_Clear();
@@ -724,29 +744,55 @@
}
}
+/* Copy values from the "locals" dict into the fast locals.
+
+ dict is an input argument containing string keys representing
+ variables names and arbitrary PyObject* as values.
+
+ map and values are input arguments. map is a tuple of strings.
+ values is an array of PyObject*. At index i, map[i] is the name of
+ the variable with value values[i]. The function copies the first
+ nmap variable from map/values into dict. If values[i] is NULL,
+ the variable is deleted from dict.
+
+ If deref is true, then the values being copied are cell variables
+ and the value is extracted from the cell variable before being put
+ in dict. If clear is true, then variables in map but not in dict
+ are set to NULL in map; if clear is false, variables missing in
+ dict are ignored.
+
+ Exceptions raised while modifying the dict are silently ignored,
+ because there is no good way to report them.
+*/
+
static void
dict_to_map(PyObject *map, Py_ssize_t nmap, PyObject *dict, PyObject **values,
- Py_ssize_t deref, int clear)
+ int deref, int clear)
{
Py_ssize_t j;
+ assert(PyTuple_Check(map));
+ assert(PyDict_Check(dict));
+ assert(PyTuple_Size(map) > nmap);
for (j = nmap; --j >= 0; ) {
PyObject *key = PyTuple_GET_ITEM(map, j);
PyObject *value = PyObject_GetItem(dict, key);
- if (value == NULL)
+ assert(PyString_Check(key));
+ /* We only care about NULLs if clear is true. */
+ if (value == NULL) {
PyErr_Clear();
+ if (!clear)
+ continue;
+ }
if (deref) {
- if (value || clear) {
- if (PyCell_GET(values[j]) != value) {
- if (PyCell_Set(values[j], value) < 0)
- PyErr_Clear();
- }
- }
- } else if (value != NULL || clear) {
- if (values[j] != value) {
- Py_XINCREF(value);
- Py_XDECREF(values[j]);
- values[j] = value;
- }
+ assert(PyCell_Check(values[j]));
+ if (PyCell_GET(values[j]) != value) {
+ if (PyCell_Set(values[j], value) < 0)
+ PyErr_Clear();
+ }
+ } else if (values[j] != value) {
+ Py_XINCREF(value);
+ Py_XDECREF(values[j]);
+ values[j] = value;
}
Py_XDECREF(value);
}
@@ -788,8 +834,18 @@
if (ncells || nfreevars) {
map_to_dict(co->co_cellvars, ncells,
locals, fast + co->co_nlocals, 1);
- map_to_dict(co->co_freevars, nfreevars,
- locals, fast + co->co_nlocals + ncells, 1);
+ /* If the namespace is unoptimized, then one of the
+ following cases applies:
+ 1. It does not contain free variables, because it
+ uses import * or is a top-level namespace.
+ 2. It is a class namespace.
+ We don't want to accidentally copy free variables
+ into the locals dict used by the class.
+ */
+ if (co->co_flags & CO_OPTIMIZED) {
+ map_to_dict(co->co_freevars, nfreevars,
+ locals, fast + co->co_nlocals + ncells, 1);
+ }
}
PyErr_Restore(error_type, error_value, error_traceback);
}