bpo-36851: Clean the frame stack if the execution ends with a return and the stack is not empty (GH-13191)
diff --git a/Lib/test/test_code.py b/Lib/test/test_code.py
index e49121e..9bf290d 100644
--- a/Lib/test/test_code.py
+++ b/Lib/test/test_code.py
@@ -130,6 +130,7 @@
import threading
import unittest
import weakref
+import opcode
try:
import ctypes
except ImportError:
@@ -379,6 +380,43 @@
tt.join()
self.assertEqual(LAST_FREED, 500)
+ @cpython_only
+ def test_clean_stack_on_return(self):
+
+ def f(x):
+ return x
+
+ code = f.__code__
+ ct = type(f.__code__)
+
+ # Insert an extra LOAD_FAST, this duplicates the value of
+ # 'x' in the stack, leaking it if the frame is not properly
+ # cleaned up upon exit.
+
+ bytecode = list(code.co_code)
+ bytecode.insert(-2, opcode.opmap['LOAD_FAST'])
+ bytecode.insert(-2, 0)
+
+ c = ct(code.co_argcount, code.co_posonlyargcount,
+ code.co_kwonlyargcount, code.co_nlocals, code.co_stacksize+1,
+ code.co_flags, bytes(bytecode),
+ code.co_consts, code.co_names, code.co_varnames,
+ code.co_filename, code.co_name, code.co_firstlineno,
+ code.co_lnotab, code.co_freevars, code.co_cellvars)
+ new_function = type(f)(c, f.__globals__, 'nf', f.__defaults__, f.__closure__)
+
+ class Var:
+ pass
+ the_object = Var()
+ var = weakref.ref(the_object)
+
+ new_function(the_object)
+
+ # Check if the_object is leaked
+ del the_object
+ assert var() is None
+
+
def test_main(verbose=None):
from test import test_code
run_doctest(test_code, verbose)
diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-05-08-11-42-06.bpo-36851.J7DiCW.rst b/Misc/NEWS.d/next/Core and Builtins/2019-05-08-11-42-06.bpo-36851.J7DiCW.rst
new file mode 100644
index 0000000..9973e4e
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2019-05-08-11-42-06.bpo-36851.J7DiCW.rst
@@ -0,0 +1,2 @@
+The ``FrameType`` stack is now correctly cleaned up if the execution ends
+with a return and the stack is not empty.
diff --git a/Python/ceval.c b/Python/ceval.c
index 4e43df2..07db1d3 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1755,7 +1755,7 @@
case TARGET(RETURN_VALUE): {
retval = POP();
assert(f->f_iblock == 0);
- goto return_or_yield;
+ goto exit_returning;
}
case TARGET(GET_AITER): {
@@ -1924,7 +1924,7 @@
/* and repeat... */
assert(f->f_lasti >= (int)sizeof(_Py_CODEUNIT));
f->f_lasti -= sizeof(_Py_CODEUNIT);
- goto return_or_yield;
+ goto exit_yielding;
}
case TARGET(YIELD_VALUE): {
@@ -1941,7 +1941,7 @@
}
f->f_stacktop = stack_pointer;
- goto return_or_yield;
+ goto exit_yielding;
}
case TARGET(POP_EXCEPT): {
@@ -3581,16 +3581,18 @@
break;
} /* main loop */
+ assert(retval == NULL);
+ assert(PyErr_Occurred());
+
+exit_returning:
+
/* Pop remaining stack entries. */
while (!EMPTY()) {
PyObject *o = POP();
Py_XDECREF(o);
}
- assert(retval == NULL);
- assert(PyErr_Occurred());
-
-return_or_yield:
+exit_yielding:
if (tstate->use_tracing) {
if (tstate->c_tracefunc) {
if (call_trace_protected(tstate->c_tracefunc, tstate->c_traceobj,