Prevent crash with a segfault on recursive repr calls (#1115)

Author: asvetlov

CHANGES/1115.bugfix

@@ -0,0 +1 @@
+Prevented crashing with a segfault when :func:`repr` is called for recursive multidicts and their proxies and views.

multidict/_multidict.c

@@ -347,10 +347,20 @@ multidict_reduce(MultiDictObject *self)
 static inline PyObject *
 multidict_repr(MultiDictObject *self)
 {
-    PyObject *name = PyObject_GetAttrString((PyObject*)Py_TYPE(self), "__name__");
-    if (name == NULL)
+    int tmp = Py_ReprEnter((PyObject *)self);
+    if (tmp < 0) {
+        return NULL;
+    }
+    if (tmp > 0) {
+        return PyUnicode_FromString("...");
+    }
+    PyObject *name = PyObject_GetAttrString((PyObject *)Py_TYPE(self), "__name__");
+    if (name == NULL) {
+        Py_ReprLeave((PyObject *)self);
         return NULL;
+    }
     PyObject *ret = pair_list_repr(&self->pairs, name, true, true);
+    Py_ReprLeave((PyObject *)self);
     Py_CLEAR(name);
     return ret;
 }

multidict/_multidict_py.py

@@ -1,4 +1,5 @@
 import enum
+import reprlib
 import sys
 from abc import abstractmethod
 from array import array
@@ -121,6 +122,7 @@ def _iter(self, version: int) -> Iterator[tuple[str, _V]]:
                 raise RuntimeError("Dictionary changed during iteration")
             yield self._keyfunc(k), v
 
+    @reprlib.recursive_repr()
     def __repr__(self) -> str:
         lst = []
         for i, k, v in self._impl._items:
@@ -254,7 +256,7 @@ def __xor__(self, other: Iterable[_T]) -> set[Union[tuple[str, _V], _T]]:
         except TypeError:
             return NotImplemented
         ret: set[Union[tuple[str, _V], _T]] = self - rgt
-        ret |= (rgt - self)
+        ret |= rgt - self
         return ret
 
     __rxor__ = __xor__
@@ -288,6 +290,7 @@ def _iter(self, version: int) -> Iterator[_V]:
                 raise RuntimeError("Dictionary changed during iteration")
             yield v
 
+    @reprlib.recursive_repr()
     def __repr__(self) -> str:
         lst = []
         for i, k, v in self._impl._items:
@@ -425,7 +428,7 @@ def __xor__(self, other: Iterable[_T]) -> set[Union[str, _T]]:
         except TypeError:
             return NotImplemented
         ret: set[Union[str, _T]] = self - rgt  # type: ignore[assignment]
-        ret |= (rgt - self)
+        ret |= rgt - self
         return ret
 
     __rxor__ = __xor__
@@ -579,6 +582,7 @@ def __contains__(self, key: object) -> bool:
                 return True
         return False
 
+    @reprlib.recursive_repr()
     def __repr__(self) -> str:
         body = ", ".join(f"'{k}': {v!r}" for i, k, v in self._impl._items)
         return f"<{self.__class__.__name__}({body})>"

multidict/_multilib/views.h

@@ -167,10 +167,20 @@ multidict_itemsview_iter(_Multidict_ViewObject *self)
 static inline PyObject *
 multidict_itemsview_repr(_Multidict_ViewObject *self)
 {
+    int tmp = Py_ReprEnter((PyObject *)self);
+    if (tmp < 0) {
+        return NULL;
+    }
+    if (tmp > 0) {
+        return PyUnicode_FromString("...");
+    }
     PyObject *name = PyObject_GetAttrString((PyObject*)Py_TYPE(self), "__name__");
-    if (name == NULL)
+    if (name == NULL) {
+        Py_ReprLeave((PyObject *)self);
         return NULL;
+    }
     PyObject *ret = pair_list_repr(&self->md->pairs, name, true, true);
+    Py_ReprLeave((PyObject *)self);
     Py_CLEAR(name);
     return ret;
 }
@@ -1034,8 +1044,9 @@ static inline PyObject *
 multidict_keysview_repr(_Multidict_ViewObject *self)
 {
     PyObject *name = PyObject_GetAttrString((PyObject*)Py_TYPE(self), "__name__");
-    if (name == NULL)
+    if (name == NULL) {
         return NULL;
+    }
     PyObject *ret = pair_list_repr(&self->md->pairs, name, true, false);
     Py_CLEAR(name);
     return ret;
@@ -1571,10 +1582,20 @@ multidict_valuesview_iter(_Multidict_ViewObject *self)
 static inline PyObject *
 multidict_valuesview_repr(_Multidict_ViewObject *self)
 {
+    int tmp = Py_ReprEnter((PyObject *)self);
+    if (tmp < 0) {
+        return NULL;
+    }
+    if (tmp > 0) {
+        return PyUnicode_FromString("...");
+    }
     PyObject *name = PyObject_GetAttrString((PyObject*)Py_TYPE(self), "__name__");
-    if (name == NULL)
+    if (name == NULL) {
+        Py_ReprLeave((PyObject *)self);
         return NULL;
+    }
     PyObject *ret = pair_list_repr(&self->md->pairs, name, false, true);
+    Py_ReprLeave((PyObject *)self);
     Py_CLEAR(name);
     return ret;
 }

tests/test_multidict.py

@@ -725,6 +725,17 @@ def test__repr__(self, cls: type[MultiDict[str]]) -> None:
 
         assert str(d) == "<%s('key': 'one', 'key': 'two')>" % _cls.__name__
 
+    def test__repr___recursive(
+        self, any_multidict_class: type[MultiDict[object]]
+    ) -> None:
+        d = any_multidict_class()
+        _cls = type(d)
+
+        d = any_multidict_class()
+        d["key"] = d
+
+        assert str(d) == "<%s('key': ...)>" % _cls.__name__
+
     def test_getall(self, cls: type[MultiDict[str]]) -> None:
         d = cls([("key", "value1")], key="value2")
 
@@ -757,6 +768,14 @@ def test_items__repr__(self, cls: type[MultiDict[str]]) -> None:
         expected = "<_ItemsView('key': 'value1', 'key': 'value2')>"
         assert repr(d.items()) == expected
 
+    def test_items__repr__recursive(
+        self, any_multidict_class: type[MultiDict[object]]
+    ) -> None:
+        d = any_multidict_class()
+        d["key"] = d.items()
+        expected = "<_ItemsView('key': <_ItemsView('key': ...)>)>"
+        assert repr(d.items()) == expected
+
     def test_keys__repr__(self, cls: type[MultiDict[str]]) -> None:
         d = cls([("key", "value1")], key="value2")
         assert repr(d.keys()) == "<_KeysView('key', 'key')>"
@@ -765,6 +784,13 @@ def test_values__repr__(self, cls: type[MultiDict[str]]) -> None:
         d = cls([("key", "value1")], key="value2")
         assert repr(d.values()) == "<_ValuesView('value1', 'value2')>"
 
+    def test_values__repr__recursive(
+        self, any_multidict_class: type[MultiDict[object]]
+    ) -> None:
+        d = any_multidict_class()
+        d["key"] = d.values()
+        assert repr(d.values()) == "<_ValuesView(<_ValuesView(...)>)>"
+
 
 class TestCIMultiDict(BaseMultiDictTest):
     @pytest.fixture(

tests/test_multidict_benchmarks.py

@@ -565,6 +565,7 @@ def _run() -> None:
         for _ in md:
             pass
 
+
 def test_iterate_multidict_keys(
     benchmark: BenchmarkFixture, any_multidict_class: Type[MultiDict[str]]
 ) -> None:
@@ -588,6 +589,7 @@ def _run() -> None:
         for _ in md.values():
             pass
 
+
 def test_iterate_multidict_items(
     benchmark: BenchmarkFixture, any_multidict_class: Type[MultiDict[str]]
 ) -> None: