bpo-38140: Make dict and weakref offsets opaque for C heap types (#16076)

* Make dict and weakref offsets opaque for C heap types

* Add news

1 files changed, 7 insertions, 1 deletions

diff --git a/Parser/asdl_c.py b/Parser/asdl_c.py
index 0b72f9e..3a9d4e6 100755
--- a/Parser/asdl_c.py
+++ b/Parser/asdl_c.py
@@ -724,6 +724,11 @@ ast_type_reduce(PyObject *self, PyObject *unused)
     return Py_BuildValue("O()", Py_TYPE(self));
 }
 
+static PyMemberDef ast_type_members[] = {
+    {"__dictoffset__", T_PYSSIZET, offsetof(AST_object, dict), READONLY},
+    {NULL}  /* Sentinel */
+};
+
 static PyMethodDef ast_type_methods[] = {
     {"__reduce__", ast_type_reduce, METH_NOARGS, NULL},
     {NULL}
@@ -740,6 +745,7 @@ static PyType_Slot AST_type_slots[] = {
     {Py_tp_setattro, PyObject_GenericSetAttr},
     {Py_tp_traverse, ast_traverse},
     {Py_tp_clear, ast_clear},
+    {Py_tp_members, ast_type_members},
     {Py_tp_methods, ast_type_methods},
     {Py_tp_getset, ast_type_getsets},
     {Py_tp_init, ast_type_init},
@@ -930,7 +936,6 @@ static int add_ast_fields(void)
         self.emit("if (init_identifiers() < 0) return 0;", 1)
         self.emit("state->AST_type = PyType_FromSpec(&AST_type_spec);", 1)
         self.emit("if (!state->AST_type) return 0;", 1)
-        self.emit("((PyTypeObject*)state->AST_type)->tp_dictoffset = offsetof(AST_object, dict);", 1)
         self.emit("if (add_ast_fields() < 0) return 0;", 1)
         for dfn in mod.dfns:
             self.visit(dfn)
@@ -1372,6 +1377,7 @@ def main(srcfile, dump_module=False):
             f.write('\n')
             f.write('#include "Python.h"\n')
             f.write('#include "%s-ast.h"\n' % mod.name)
+            f.write('#include "structmember.h"\n')
             f.write('\n')
 
             generate_module_def(f, mod)