[mypyc] Calling tp_finalize from tp_dealloc.

mypyc/codegen/emitclass.py

@@ -205,6 +205,7 @@ def generate_class(cl: ClassIR, module: str, emitter: Emitter) -> None:
 
     setup_name = f"{name_prefix}_setup"
     new_name = f"{name_prefix}_new"
+    finalize_name = f"{name_prefix}_finalize"
     members_name = f"{name_prefix}_members"
     getseters_name = f"{name_prefix}_getseters"
     vtable_name = f"{name_prefix}_vtable"
@@ -226,6 +227,10 @@ def generate_class(cl: ClassIR, module: str, emitter: Emitter) -> None:
         fields["tp_dealloc"] = f"(destructor){name_prefix}_dealloc"
         fields["tp_traverse"] = f"(traverseproc){name_prefix}_traverse"
         fields["tp_clear"] = f"(inquiry){name_prefix}_clear"
+    # Populate .tp_finalize and generate a finalize method only if __del__ is defined for this class.
+    del_method = next((e.method for e in cl.vtable_entries if e.name == "__del__"), None)
+    if del_method:
+        fields["tp_finalize"] = f"(destructor){finalize_name}"
     if needs_getseters:
         fields["tp_getset"] = getseters_name
     fields["tp_methods"] = methods_name
@@ -308,6 +313,9 @@ def emit_line() -> None:
         emit_line()
         generate_dealloc_for_class(cl, dealloc_name, clear_name, emitter)
         emit_line()
+        if del_method:
+            generate_finalize_for_class(del_method, finalize_name, emitter)
+            emit_line()
 
         if cl.allow_interpreted_subclasses:
             shadow_vtable_name: str | None = generate_vtables(
@@ -779,6 +787,9 @@ def generate_dealloc_for_class(
     emitter.emit_line("static void")
     emitter.emit_line(f"{dealloc_func_name}({cl.struct_name(emitter.names)} *self)")
     emitter.emit_line("{")
+    emitter.emit_line("if (Py_TYPE(self)->tp_finalize) {")
+    emitter.emit_line("    Py_TYPE(self)->tp_finalize((PyObject *)self);")
+    emitter.emit_line("}")
     emitter.emit_line("PyObject_GC_UnTrack(self);")
     # The trashcan is needed to handle deep recursive deallocations
     emitter.emit_line(f"CPy_TRASHCAN_BEGIN(self, {dealloc_func_name})")
@@ -788,6 +799,22 @@ def generate_dealloc_for_class(
     emitter.emit_line("}")
 
 
+def generate_finalize_for_class(
+    del_method: FuncIR, finalize_func_name: str, emitter: Emitter
+) -> None:
+    emitter.emit_line("static void")
+    emitter.emit_line(f"{finalize_func_name}(PyObject *self)")
+    emitter.emit_line("{")
+    emitter.emit_line(
+        "{}{}{}(self);".format(
+            emitter.get_group_prefix(del_method.decl),
+            NATIVE_PREFIX,
+            del_method.cname(emitter.names),
+        )
+    )
+    emitter.emit_line("}")
+
+
 def generate_methods_table(cl: ClassIR, name: str, emitter: Emitter) -> None:
     emitter.emit_line(f"static PyMethodDef {name}[] = {{")
     for fn in cl.methods.values():

mypyc/test-data/run-classes.test

@@ -2719,3 +2719,29 @@ print(native.A(ints=[1, -17]).ints)
 
 [out]
 \[1, -17]
+
+[case testDel]
+class A:
+    def __del__(self):
+        print("deleting A...")
+
+class B:
+    def __del__(self):
+        print("deleting B...")
+
+class C(B):
+    def __init__(self):
+        self.a = A()
+
+    def __del__(self):
+        print("deleting C...")
+        super().__del__()
+
+[file driver.py]
+import native
+native.C()
+
+[out]
+deleting C...
+deleting B...
+deleting A...