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- Subject: Re: Why is the stack cleared on panic?
- From: Julio Merino <jmmv84@...>
- Date: Mon, 10 Jan 2011 16:33:56 +0000
On Mon, Jan 10, 2011 at 4:21 PM, Drake Wilson <firstname.lastname@example.org> wrote:
> Quoth Julio Merino <email@example.com>, on 2011-01-10 15:50:45 +0000:
>> void safe_gettable(lua_State* s, const int index)
>> if (setjmp(buf) == 0)
>> lua_gettable(s, index);
>> throw error('Uh oh, lua_gettable failed');
> This doesn't answer your original question, but lua_atpanic isn't for
> that. The above fails if safe_gettable is ever called inside a pcall.
> The error will be propagated immediately to the site of the pcall, and
> the panic handler does not run. Further, your stack has already been
> unwound, and depending on the platform, destructors may not get called
> and such. Essentially this is the "stock Lua doesn't play well with
> C++ unwinding" bit. (Unfortunately, I don't immediately recall a good
> solution that works in your case; perhaps someone else does.)
Ah, very true -- had missed that. Well, I guess this indirectly
answers my question too.
What I'm currently doing is to wrap the unsafe call in a tiny C
function of its own and then call it explicitly with lua_pcall.
(Unfortunately, that has overhead and can still fail due to
out-of-memory errors because the lua_push* functions required for such
setup are not protected...)
1: See the lua::state::get_table method (line 154) in