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gh-104404: fix crasher with nested comprehensions plus lambdas #104442

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merged 1 commit into from
May 13, 2023
Merged

gh-104404: fix crasher with nested comprehensions plus lambdas #104442

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8 changes: 8 additions & 0 deletions Lib/test/test_listcomps.py
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Original file line number Diff line number Diff line change
Expand Up @@ -338,6 +338,14 @@ def test_nested_3(self):
outputs = {"y": [1, 3, 5]}
self._check_in_scopes(code, outputs)

def test_nested_4(self):
code = """
items = [([lambda: x for x in range(2)], lambda: x) for x in range(3)]
out = [([fn() for fn in fns], fn()) for fns, fn in items]
"""
outputs = {"out": [([1, 1], 2), ([1, 1], 2), ([1, 1], 2)]}
self._check_in_scopes(code, outputs)

def test_nameerror(self):
code = """
[x for x in [1]]
Expand Down
21 changes: 14 additions & 7 deletions Python/symtable.c
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Original file line number Diff line number Diff line change
Expand Up @@ -575,7 +575,8 @@ is_free_in_any_child(PySTEntryObject *entry, PyObject *key)

static int
inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
PyObject *scopes, PyObject *comp_free)
PyObject *scopes, PyObject *comp_free,
PyObject *promote_to_cell)
{
PyObject *k, *v;
Py_ssize_t pos = 0;
Expand Down Expand Up @@ -611,7 +612,9 @@ inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
// cell vars in comprehension that are locals in outer scope
// must be promoted to cell so u_cellvars isn't wrong
if (scope == CELL && ste->ste_type == FunctionBlock) {
SET_SCOPE(scopes, k, scope);
if (PySet_Add(promote_to_cell, k) < 0) {
return 0;
}
}

// free vars in comprehension that are locals in outer scope can
Expand All @@ -638,7 +641,7 @@ inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
*/

static int
analyze_cells(PyObject *scopes, PyObject *free)
analyze_cells(PyObject *scopes, PyObject *free, PyObject *promote_to_cell)
{
PyObject *name, *v, *v_cell;
int success = 0;
Expand All @@ -653,7 +656,7 @@ analyze_cells(PyObject *scopes, PyObject *free)
scope = PyLong_AS_LONG(v);
if (scope != LOCAL)
continue;
if (!PySet_Contains(free, name))
if (!PySet_Contains(free, name) && !PySet_Contains(promote_to_cell, name))
continue;
/* Replace LOCAL with CELL for this name, and remove
from free. It is safe to replace the value of name
Expand Down Expand Up @@ -803,7 +806,7 @@ analyze_block(PySTEntryObject *ste, PyObject *bound, PyObject *free,
PyObject *global)
{
PyObject *name, *v, *local = NULL, *scopes = NULL, *newbound = NULL;
PyObject *newglobal = NULL, *newfree = NULL;
PyObject *newglobal = NULL, *newfree = NULL, *promote_to_cell = NULL;
PyObject *temp;
int success = 0;
Py_ssize_t i, pos = 0;
Expand Down Expand Up @@ -835,6 +838,9 @@ analyze_block(PySTEntryObject *ste, PyObject *bound, PyObject *free,
newbound = PySet_New(NULL);
if (!newbound)
goto error;
promote_to_cell = PySet_New(NULL);
if (!promote_to_cell)
goto error;

/* Class namespace has no effect on names visible in
nested functions, so populate the global and bound
Expand Down Expand Up @@ -915,7 +921,7 @@ analyze_block(PySTEntryObject *ste, PyObject *bound, PyObject *free,
goto error;
}
if (inline_comp) {
if (!inline_comprehension(ste, entry, scopes, child_free)) {
if (!inline_comprehension(ste, entry, scopes, child_free, promote_to_cell)) {
Py_DECREF(child_free);
goto error;
}
Expand Down Expand Up @@ -946,7 +952,7 @@ analyze_block(PySTEntryObject *ste, PyObject *bound, PyObject *free,
}

/* Check if any local variables must be converted to cell variables */
if (ste->ste_type == FunctionBlock && !analyze_cells(scopes, newfree))
if (ste->ste_type == FunctionBlock && !analyze_cells(scopes, newfree, promote_to_cell))
goto error;
else if (ste->ste_type == ClassBlock && !drop_class_free(ste, newfree))
goto error;
Expand All @@ -966,6 +972,7 @@ analyze_block(PySTEntryObject *ste, PyObject *bound, PyObject *free,
Py_XDECREF(newbound);
Py_XDECREF(newglobal);
Py_XDECREF(newfree);
Py_XDECREF(promote_to_cell);
if (!success)
assert(PyErr_Occurred());
return success;
Expand Down