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bpo-33622: Add checks for exceptions leaks in the garbage collector. #7126

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Merged
merged 3 commits into from
May 29, 2018
Merged

bpo-33622: Add checks for exceptions leaks in the garbage collector. #7126

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27f2b83
bpo-33622: Add checks for exceptions leaks in the garbage collector.
serhiy-storchaka May 24, 2018
032a0ba
Address review comments.
serhiy-storchaka May 28, 2018
8de8f20
Check and silence errors in tp_clear.
serhiy-storchaka May 29, 2018
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27 changes: 23 additions & 4 deletions Modules/gcmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -654,6 +654,7 @@ handle_legacy_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
{
PyGC_Head *gc = finalizers->gc.gc_next;

assert(!PyErr_Occurred());
if (_PyRuntime.gc.garbage == NULL) {
_PyRuntime.gc.garbage = PyList_New(0);
if (_PyRuntime.gc.garbage == NULL)
Expand All @@ -663,8 +664,10 @@ handle_legacy_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
PyObject *op = FROM_GC(gc);
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Usually, when I start to add assert(!PyErr_Occurred()), I like to add the assertion at the function entry and exit. Here it would avoid to remove an exception, since you add PyErr_Clear(). Currently, it's non obvious that the function must not be called with an exception set. An assertion would make it obvious ;-)


if ((_PyRuntime.gc.debug & DEBUG_SAVEALL) || has_legacy_finalizer(op)) {
if (PyList_Append(_PyRuntime.gc.garbage, op) < 0)
if (PyList_Append(_PyRuntime.gc.garbage, op) < 0) {
PyErr_Clear();
break;
}
}
}

Expand Down Expand Up @@ -701,6 +704,7 @@ finalize_garbage(PyGC_Head *collectable)
_PyGCHead_SET_FINALIZED(gc, 1);
Py_INCREF(op);
finalize(op);
assert(!PyErr_Occurred());
Py_DECREF(op);
}
}
Expand Down Expand Up @@ -748,17 +752,26 @@ delete_garbage(PyGC_Head *collectable, PyGC_Head *old)
{
inquiry clear;

assert(!PyErr_Occurred());
while (!gc_list_is_empty(collectable)) {
PyGC_Head *gc = collectable->gc.gc_next;
PyObject *op = FROM_GC(gc);

if (_PyRuntime.gc.debug & DEBUG_SAVEALL) {
PyList_Append(_PyRuntime.gc.garbage, op);
assert(_PyRuntime.gc.garbage != NULL);
if (PyList_Append(_PyRuntime.gc.garbage, op) < 0) {
PyErr_Clear();
}
}
else {
if ((clear = Py_TYPE(op)->tp_clear) != NULL) {
Py_INCREF(op);
clear(op);
(void) clear(op);
if (PyErr_Occurred()) {
PySys_WriteStderr("Exception ignored in tp_clear of "
"%.50s\n", Py_TYPE(op)->tp_name);
PyErr_WriteUnraisable(NULL);
}
Py_DECREF(op);
}
}
Expand Down Expand Up @@ -974,6 +987,7 @@ collect(int generation, Py_ssize_t *n_collected, Py_ssize_t *n_uncollectable,
if (PyDTrace_GC_DONE_ENABLED())
PyDTrace_GC_DONE(n+m);

assert(!PyErr_Occurred());
return n+m;
}

Expand All @@ -987,11 +1001,12 @@ invoke_gc_callback(const char *phase, int generation,
Py_ssize_t i;
PyObject *info = NULL;

assert(!PyErr_Occurred());
/* we may get called very early */
if (_PyRuntime.gc.callbacks == NULL)
return;
/* The local variable cannot be rebound, check it for sanity */
assert(_PyRuntime.gc.callbacks != NULL && PyList_CheckExact(_PyRuntime.gc.callbacks));
assert(PyList_CheckExact(_PyRuntime.gc.callbacks));
if (PyList_GET_SIZE(_PyRuntime.gc.callbacks) != 0) {
info = Py_BuildValue("{sisnsn}",
"generation", generation,
Expand All @@ -1015,6 +1030,7 @@ invoke_gc_callback(const char *phase, int generation,
Py_DECREF(cb);
}
Py_XDECREF(info);
assert(!PyErr_Occurred());
}

/* Perform garbage collection of a generation and invoke
Expand All @@ -1024,9 +1040,11 @@ static Py_ssize_t
collect_with_callback(int generation)
{
Py_ssize_t result, collected, uncollectable;
assert(!PyErr_Occurred());
invoke_gc_callback("start", generation, 0, 0);
result = collect(generation, &collected, &uncollectable, 0);
invoke_gc_callback("stop", generation, collected, uncollectable);
assert(!PyErr_Occurred());
return result;
}

Expand Down Expand Up @@ -1592,6 +1610,7 @@ _PyGC_CollectNoFail(void)
{
Py_ssize_t n;

assert(!PyErr_Occurred());
/* Ideally, this function is only called on interpreter shutdown,
and therefore not recursively. Unfortunately, when there are daemon
threads, a daemon thread can start a cyclic garbage collection
Expand Down