bpo-44449: faulthandler don't modify frame refcnt (GH-27850)
Fix a crash in the signal handler of the faulthandler module: no
longer modify the reference count of frame objects.
diff --git a/Python/traceback.c b/Python/traceback.c
index f7dc5ad..88ffc01 100644
--- a/Python/traceback.c
+++ b/Python/traceback.c
@@ -796,7 +796,10 @@ dump_traceback(int fd, PyThreadState *tstate, int write_header)
PUTS(fd, "Stack (most recent call first):\n");
}
- frame = PyThreadState_GetFrame(tstate);
+ // Use a borrowed reference. Avoid Py_INCREF/Py_DECREF, since this function
+ // can be called in a signal handler by the faulthandler module which must
+ // not modify Python objects.
+ frame = tstate->frame;
if (frame == NULL) {
PUTS(fd, "<no Python frame>\n");
return;
@@ -805,17 +808,14 @@ dump_traceback(int fd, PyThreadState *tstate, int write_header)
depth = 0;
while (1) {
if (MAX_FRAME_DEPTH <= depth) {
- Py_DECREF(frame);
PUTS(fd, " ...\n");
break;
}
if (!PyFrame_Check(frame)) {
- Py_DECREF(frame);
break;
}
dump_frame(fd, frame);
- PyFrameObject *back = PyFrame_GetBack(frame);
- Py_DECREF(frame);
+ PyFrameObject *back = frame->f_back;
if (back == NULL) {
break;