Re: Strange intermittent LuaJIT errors (likely my fault)

[Alexander Gladysh <agladysh@...>]

On Fri, Apr 6, 2012 at 13:11, Alexander Gladysh <agladysh@gmail.com> wrote:
> On Fri, Apr 6, 2012 at 11:10, Alexander Gladysh <agladysh@gmail.com> wrote:
>> On Fri, Apr 6, 2012 at 08:37, Alexander Gladysh <agladysh@gmail.com> wrote:
>>> On Thu, Apr 5, 2012 at 01:54, Alexander Gladysh <agladysh@gmail.com> wrote:
>>
>>>> While trying to optimize my Lua serialization library, luatexts[1],
>>>> I've stumbled upon this strange crash in LJ2:
>>>>
>>>> ./luajit: /usr/local/share/lua/5.1/lua-nucleo/tdeepequals.lua:0:
>>>> attempt to index a boolean value
>>>> stack traceback:
>>>>        /usr/local/share/lua/5.1/lua-nucleo/tdeepequals.lua: in function 'tdeepequals'
>>>>        /usr/local/share/lua/5.1/lua-nucleo/ensure.lua:318: in function
>>>> 'ensure_returns'
>>>>        test/test.lua:2238: in main chunk
>>>>        [C]: ?
>>>>
>>>> Note strangely missing line info. This happens during generative test
>>>> suite when I'm trying to load mutated data — so all kinds of bad
>>>> things may happen.
>>>
>>> Here is another kind of crash:
>>>
>>> luajit2: /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:192:
>>> attempt to get length of local 'keys1' (a function value)
>>> stack traceback:
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:192: in function 'tmore'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:186: in function 'tmore'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:186: in function 'tmore'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:186: in function 'tmore'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:207: in function 'tmore'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:203: in function 'tmore'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:107: in function
>>> </usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:104>
>>>        [C]: in function 'table_sort'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:199: in function 'tmore'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:203: in function 'tmore'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:203: in function 'tmore'
>>>        /usr/local/share/lua/5.1//lua-nucleo/tdeepequals.lua:227: in function
>>> 'tdeepequals'
>>>        /usr/local/share/lua/5.1//lua-nucleo/ensure.lua:318: in function
>>> 'ensure_returns'
>>>        test/test.lua:2238: in main chunk
>>>        [C]: ?
>>
>> Ugh, that's a nasty one...
>>
>> I was able to reproduce this crash outside of my mutation data set, so
>> it is less likely that it is some kind of memory corruption on my
>> side. Since the crash is intermittent, it is also less likely that my
>> code breaks Lua state somehow. (But, of course, all that is still
>> possible.)
>>
>> Wrapping code in xpcall or adding some additional output seems to
>> prevent this bug from appearing...

> I prepared a dataset to reproduce the crash:

I was able to reproduce the crash without my C module (by rewriting
its functionality in Lua), so this looks like bug in LJ2 indeed.
(Since tdeepequals or other code does not employ random and the bug is
intermittent, I doubt that the problem is with my code.)

Here is how it looks:

Sat Apr  7 01:31:41 MSK 2012 ERROR 3 BEGIN (iteration 6)
Sat Apr  7 01:31:41 MSK 2012 strace:
open("data/00000447.luatexts", O_RDONLY|O_LARGEFILE) = 3
Sat Apr  7 01:31:41 MSK 2012 stderr:
replay.lua: PREFIX: data OFFSET: 1 MODE: lua
./luajit: ./lua-nucleo/tdeepequals.lua:0: attempt to index a boolean value
stack traceback:
	./lua-nucleo/tdeepequals.lua: in function 'tdeepequals'
	./lua-nucleo/ensure.lua:318: in function 'ensure_returns'
	../../etc/replay.lua:96: in main chunk
	[C]: ?
Sat Apr  7 01:31:41 MSK 2012 ERROR 3 END

Another one:

Sat Apr  7 01:34:36 MSK 2012 ERROR 3 BEGIN (iteration 20)
Sat Apr  7 01:34:36 MSK 2012 strace:
open("data/00000155.luatexts", O_RDONLY|O_LARGEFILE) = 3
Sat Apr  7 01:34:36 MSK 2012 stderr:
replay.lua: PREFIX: data OFFSET: 1 MODE: lua
./luajit: ./lua-nucleo/tdeepequals.lua:192: attempt to get length of
local 'keys1' (a number value)
stack traceback:
	./lua-nucleo/tdeepequals.lua:192: in function 'tmore'
	./lua-nucleo/tdeepequals.lua:186: in function 'tmore'
	./lua-nucleo/tdeepequals.lua:227: in function 'tdeepequals'
	./lua-nucleo/ensure.lua:318: in function 'ensure_returns'
	../../etc/replay.lua:96: in main chunk
	[C]: ?
Sat Apr  7 01:34:36 MSK 2012 ERROR 3 END

To reproduce (note that the current code is in master branch now):

# install strace
# install luarocks
sudo luarocks install luafilesystem
git clone git://github.com/agladysh/luatexts.git
cd test/crash
./reproduce.sh lua

(Run `./reproduce.sh c` for C version.)

Mike, any help?

Thanks,
Alexander.