On Thu, Jun 13, 2013 at 1:17 AM, Paul K paulclin...@yahoo.com wrote:
Hi John,
I got several reports (from the same machine) of crashes in my
application when a user types something in wxSTC control. It's
difficult to reproduce and seems to happen infrequently, but the
captured stack trace points to wxLuaState::LuaPCall call. This is
running wxlua 2.8.12.2 and wxwidgets 2.9.5 (compiled at the end of
April).
The wxLua C++ event handler callback uses LuaPCall() to run your Lua event
handler function for the wxStyledTextEvent. From the stack it looks like
the event is a char added event.
I'm including the top part of the stack trace below (the full stack is
in this ticket:
https://github.com/pkulchenko/ZeroBraneStudio/issues/164), but there
are several odd things I noticed.
1. The trace shows lua51!lua_yield call after wxLuaState::LuaPCall
call, but I don't see any lua_yield calls in that function.
lua_yield is a coroutine function, are you running coroutines? If so, then
Lua will be swapping lua_States in and out and pausing them whenever it
wants to, making the stack seem very strange.
You're not trying to install event handlers in a coroutine are you? As we
discussed, that's always a bad idea.
2. The trace shows wxProgressDialog_delete_function call in the stack,
but I don't use that component anywhere in the application; the stack
looks wrong at that point as I wouldn't expect any wxProgressDialog
call from lua_getinfo.
Did you ever create a wxProgressDialog? The Lua garbage collector may
simply be running and finally getting around to deleting it.
3. The crash seems to be in this fragment in wxlua/wxlcallb.cpp:
// Don't track the wxEvent since we don't own it and tracking
it
// causes clashes in the object registry table since many can
be
// created and deleted and the mem address is resused by C++.
wxlState.wxluaT_PushUserDataType(event, event_wxl_type, false);
wxlState.LuaPCall(1, 0); // one input no returns
What events are being referred to here as we don't own it? Is it
possible to check for these events explicitly? Any idea why it may be
crashing here and how to avoid this? Thank you!
We meaning, wxLua/Lua, does not own the allocated memory for the wxEvent
class so even though wxLua pushes it onto the Lua stack wxLua/Lua will not
try to delete it when the function ends. Think of wxMouseEvents, if you
have a very simple event handler function it may happen that each
successive wxMouseEvent will use the same memory. Therefore, wxLua cannot
track the event since the Lua garbage collector can be slow to clean up
and we get seemingly duplicate tracked items, but the first one is long
gone, this is merely book keeping.
The event is a wxStyledTextEvent based on the stack.
Can you rebuild in debug mode? The stack should have line numbers which
will clear things up. Everything is normal up to LuaPCall, but then I
presume you're running a coroutine that's calling the lua_yield, and wxLua
does use lua_getinfo for a few things so that may be normal, but the
lua_close is very wrong unless you're closing a coroutine, perhaps the
coroutine had a wxProgressDialog and that's why it's getting deleted at
this point? I can't imagine who's calling AddPendingEvent though, are you?
In any case, if you do create a wxProgressDialog I suggest that you
explicitly call dlg:Destroy() on it to ensure that it's cleaned up
immediately instead of waiting for the garbage collector.
Regards,
John
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0028f1c0 01f7c151
