[3.14] gh-145701: Fix __classdict__ & __conditional_annotations__ in class-scope inlined comprehensions (GH-145702) (#145710)

miss-islington · StanFromIreland · web-flow · commit 0db2beee6b35 · 2026-03-09T20:26:52.000Z
(cherry picked from commit 63eaaf9) Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com> * Add `:oss-fuzz:` supports Backports part of 255e79f. Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
diff --git a/Doc/conf.py b/Doc/conf.py
@@ -554,6 +554,7 @@
 # mapping unique short aliases to a base URL and a prefix.
 # https://www.sphinx-doc.org/en/master/usage/extensions/extlinks.html
 extlinks = {
+    "oss-fuzz": ("https://issues.oss-fuzz.com/issues/%s", "#%s"),
     "pypi": ("https://pypi.org/project/%s/", "%s"),
     "source": (SOURCE_URI, "%s"),
 }
diff --git a/Lib/test/test_listcomps.py b/Lib/test/test_listcomps.py
@@ -180,6 +180,18 @@ def test_references___class___defined(self):
                 code, outputs={"res": [2]}, scopes=["module", "function"])
         self._check_in_scopes(code, raises=NameError, scopes=["class"])
 
+    def test_references___classdict__(self):
+        code = """
+            class i: [__classdict__ for x in y]
+        """
+        self._check_in_scopes(code, raises=NameError)
+
+    def test_references___conditional_annotations__(self):
+        code = """
+            class i: [__conditional_annotations__ for x in y]
+        """
+        self._check_in_scopes(code, raises=NameError)
+
     def test_references___class___enclosing(self):
         code = """
             __class__ = 2
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-03-09-18-52-03.gh-issue-145701.79KQyO.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-03-09-18-52-03.gh-issue-145701.79KQyO.rst
@@ -0,0 +1,3 @@
+Fix :exc:`SystemError` when ``__classdict__`` or
+``__conditional_annotations__`` is in a class-scope inlined comprehension.
+Found by OSS Fuzz in :oss-fuzz:`491105000`.
diff --git a/Python/symtable.c b/Python/symtable.c
@@ -806,6 +806,8 @@ inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
     PyObject *k, *v;
     Py_ssize_t pos = 0;
     int remove_dunder_class = 0;
+    int remove_dunder_classdict = 0;
+    int remove_dunder_cond_annotations = 0;
 
     while (PyDict_Next(comp->ste_symbols, &pos, &k, &v)) {
         // skip comprehension parameter
@@ -828,15 +830,27 @@ inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
         if (existing == NULL && PyErr_Occurred()) {
             return 0;
         }
-        // __class__ is never allowed to be free through a class scope (see
+        // __class__, __classdict__ and __conditional_annotations__ are
+        // never allowed to be free through a class scope (see
         // drop_class_free)
         if (scope == FREE && ste->ste_type == ClassBlock &&
-                _PyUnicode_EqualToASCIIString(k, "__class__")) {
+                (_PyUnicode_EqualToASCIIString(k, "__class__") ||
+                 _PyUnicode_EqualToASCIIString(k, "__classdict__") ||
+                 _PyUnicode_EqualToASCIIString(k, "__conditional_annotations__"))) {
             scope = GLOBAL_IMPLICIT;
             if (PySet_Discard(comp_free, k) < 0) {
                 return 0;
             }
-            remove_dunder_class = 1;
+
+            if (_PyUnicode_EqualToASCIIString(k, "__class__")) {
+                remove_dunder_class = 1;
+            }
+            else if (_PyUnicode_EqualToASCIIString(k, "__conditional_annotations__")) {
+                remove_dunder_cond_annotations = 1;
+            }
+            else {
+                remove_dunder_classdict = 1;
+            }
         }
         if (!existing) {
             // name does not exist in scope, copy from comprehension
@@ -876,6 +890,12 @@ inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
     if (remove_dunder_class && PyDict_DelItemString(comp->ste_symbols, "__class__") < 0) {
         return 0;
     }
+    if (remove_dunder_classdict && PyDict_DelItemString(comp->ste_symbols, "__classdict__") < 0) {
+        return 0;
+    }
+    if (remove_dunder_cond_annotations && PyDict_DelItemString(comp->ste_symbols, "__conditional_annotations__") < 0) {
+        return 0;
+    }
     return 1;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -554,6 +554,7 @@`
`554`	`554`	`# mapping unique short aliases to a base URL and a prefix.`
`555`	`555`	`# https://www.sphinx-doc.org/en/master/usage/extensions/extlinks.html`
`556`	`556`	`extlinks = {`
	`557`	`+ "oss-fuzz": ("https://issues.oss-fuzz.com/issues/%s", "#%s"),`
`557`	`558`	`"pypi": ("https://pypi.org/project/%s/", "%s"),`
`558`	`559`	`"source": (SOURCE_URI, "%s"),`
`559`	`560`	`}`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+Fix :exc:`SystemError` when ``__classdict__`` or
	`2`	+``__conditional_annotations__`` is in a class-scope inlined comprehension.
	`3`	+Found by OSS Fuzz in :oss-fuzz:`491105000`.