[mypyc] Release new instances when __init__ raises (#21248)

hauntsaninja · web-flow · commit ba4f01807ade · 2026-04-16T13:23:18.000+01:00
Found by @devdanzin
diff --git a/mypyc/codegen/emitclass.py b/mypyc/codegen/emitclass.py
@@ -836,7 +836,8 @@ def generate_new_for_class(
         emitter.emit_line(
             f"PyObject *ret = {PREFIX}{init_fn.cname(emitter.names)}(self, args, kwds);"
         )
-        emitter.emit_lines("if (ret == NULL)", "    return NULL;")
+        emitter.emit_lines("if (ret == NULL) {", "    Py_DECREF(self);", "    return NULL;", "}")
+        emitter.emit_line("Py_DECREF(ret);")
         emitter.emit_line("return self;")
     emitter.emit_line("}")
 

Original file line number	Diff line number	Diff line change
`@@ -836,7 +836,8 @@ def generate_new_for_class(`
`836`	`836`	`emitter.emit_line(`
`837`	`837`	`f"PyObject *ret = {PREFIX}{init_fn.cname(emitter.names)}(self, args, kwds);"`
`838`	`838`	`)`
`839`		`- emitter.emit_lines("if (ret == NULL)", " return NULL;")`
	`839`	`+ emitter.emit_lines("if (ret == NULL) {", " Py_DECREF(self);", " return NULL;", "}")`
	`840`	`+ emitter.emit_line("Py_DECREF(ret);")`
`840`	`841`	`emitter.emit_line("return self;")`
`841`	`842`	`emitter.emit_line("}")`
`842`	`843`