Re: Debugging crashes on GC

["Alexander Gladysh" <agladysh@...>]

> > I've assigned this coroutine to global Lua variable. The
> > crashes are still here.

> > Is there any method to debug GC crashes except that trying to
> > randomly guess which Lua object got collected?

> I am hardly an expert on this, but if it is userdata you suspect then
> what I do is make sure all userdata objects have a __gc function
> registered in their metatable. Then from that function I print a log
> message reporting the address of the object getting collected. I match
> this to messages logged when the userdata object is created. I have
> found this to help with both problems of objects getting collected when
> I don't want them to and the issue of making sure objects are collected
> when they should be.

That's a good idea, thank you. But unfortunately all my userdata
objects are Luabind objects. They seem to have their own __gc
metamethod.

> Unfortunately I don't know of a way to track the lifecycle of lua
> objects other than userdata.

I think it is possible to set __gc metamethod to table objects from
Lua, and I've read somewhere that you can set metatable to any Lua
data type from C. Can't say if __gc would get called in the case with,
say, numbers though... but we'd need to inspect thread collection, not
numbers.

> If you can modify the lua source in your
> project it might be possible to change the garbage collection code to
> report some information on objects as they get collected.

Yes, we can modify Lua sources in our project (can't say that we eager
to do so).

I do not think that it is userdata (not the visible side of problem
anyway). Since rawgeti gets corrupted Lua state as parameter, it looks
like that it is some Lua thread (coroutine) gets collected. Have I do
hack Lua sources to add logging on construction/collection of all Lua
threads, or I can track it interactively in VC 8 debugger somehow?

Thank you,
Alexander.