Am 01.10.2014 um 14:40 schrieb Rob Hoelz:
> Hello Awesome developers,
Hi Rob,
> I've encountered an interesting behavior in Awesome while playing with
> coroutines and timers (in an effort to develop a framework where one
> can write synchronous-looking code that runs in an asynchronous
> fashion). In short, I am able to make Awesome segfault when using
> certain Awesome API functions from within a coroutine.
At least here it doesn't segfault, but die from an unprotected Lua error. That
may not make much of a difference to you, but to me it's quite a big one.
> Here's some example code:
>
> local sd = require 'sleep-dealer'
> local notify = require('naughty').notify
>
> sd.tuck_in(function()
> for i = 1, 5 do
> sd.sleep(1)
> notify {
> title = 'Alert!',
> text = tostring(i),
> }
> end
> end)
Urgh, complicated. Thanks for your simpler example from the other mail in this
thread:
local co = coroutine.create(function()
notify { title = 'Alert!', text = 'hello' }
end)
coroutine.resume(co)
[...]
> When naughty.notify is called, a segfault occurs. I've determined that
> this is because globalconf.L is used in a lot of Lua API calls.
> Sometimes the Lua state passed into a function is really the state
> corresponding to a coroutine, so the states don't match and Lua panics.
Yeah, but nothing crashes! :P
> I bring this up here on the mailing list rather than fixing it myself
> or filing a bug because I wanted to take the pulse of the developer
> community on whether this is a true bug or if this is doing something
> with Awesome that it wasn't intended for. If it's the latter, I can
> let the matter rest; if it's the former, I would be happy to contribute
> a patch that fixes the problem.
Sorry for not replying sooner. I've been busy. Thanks to you I learned something
about Lua and I already went ahead and fixed the problem. I went through all
uses of globalconf.L in awesome and checked them:
https://github.com/awesomeWM/awesome/commit/f957764e522253007dbb7ecf5abf869bd38b70e2
https://github.com/awesomeWM/awesome/commit/4cfea189f04e3133c87b36ef26229abaa4ab7eb2
https://github.com/awesomeWM/awesome/commit/d668268591c9854184583fffe58b945f8a9398d9
https://github.com/awesomeWM/awesome/commit/da15317ac2e299f3c1b3833b2c5b198d2d7df5ab
If anyone has a good idea on how to make it harder to introduce this kind of
error in the future, please speak up. I guess it would at least be a good idea
to never use globalconf.L directly and instead force the code to create a local
variable lua_State *L and use that. That way, there are less places where
globalconf.L is used plus the compiler warns if there are two variables with
name "L" in scope... I guess I'll implement that.
Cheers,
Uli
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