Hi,
I'm Yash, currently working on the PostgreSQL plv8 extension, which
integrates the V8 JavaScript engine. During one of the regression tests
[1], the following query results in an error and causes the process to hang
indefinitely:
SELECT caller(10, 3);
ERROR: javascript function is not found for "sqlf"
CONTEXT: caller() LINE 8: func = plv8.find_function("sqlf");
While debugging the V8 engine, I made the following observations:
1.
In VisitStack() (isolate.cc), the following loop hangs:
for (StackFrameIterator it(isolate); !it.done(); it.Advance()) {
2.
Diving deeper, inside StackFrameIterator::Advance() (frames.cc [2]), the
loop:
while (!it.done()) { it.Advance(); }
gets stuck because of this line:
handler_ = handler_->next();
It appears that handler_->next() is pointing back to handler_ itself,
creating a cycle and causing an infinite loop.
Could someone help me understand why handler_->next() could end up pointing
to itself, instead of being nullptr? I'm trying to trace the root cause of
this corrupted/cyclic stack handler state.
Any guidance on how to further debug this would be appreciated.
References:-
[1] https://github.com/plv8/plv8/blob/r3.2/sql/plv8.sql#L403
[2] https://github.com/v8/v8/blob/main/src/execution/frames.cc#L119
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