Re: [LPeg] intermittent stack exhaustion

[Sebastian Cato <seb.cato@...>]

Hello again,

I've managed to reduce the test case to something a bit more managable:

#!/usr/bin/env lua
lpeg = require "lpeg"

print(lpeg.P{
  "Line";
  P = lpeg.P"a",
  Q = lpeg.V"P",
  Line = (lpeg.P"x" * lpeg.C(1-lpeg.V"P")),
}:match("xx"))

I've also tested it on FreeBSD with Lua 5.2.4 and LPeg 1.0.0 with the
same intermittent segfault happening.

//Sebastian Cato

On Sun, Sep 11, 2016 at 6:22 PM, Sebastian Cato <seb.cato@gmail.com> wrote:
> Sorry, hit enter too early. Should make a habit of filling out the address last.
>
> So, I started writing a markdown (or a dialect thereof) to HTML
> translator to play around with LPeg. The code is at:
>
> https://github.com/sebcat/lpeg-markdown
>
> While running markdown_test.lua, the interpreter crashes intermittently.
>
> a commit that exhibits this problem, should the repo change:
>
> git checkout c82794f8f2637ac4161f21113bbf4f23aa34906e
>
> platform info:
>
> $ uname -a
> Linux genesis 4.6.6-200.fc23.x86_64 #1 SMP Wed Aug 10 23:13:35 UTC
> 2016 x86_64 x86_64 x86_64 GNU/Linux
> $ lua -v
> Lua 5.3.3  Copyright (C) 1994-2016 Lua.org, PUC-Rio
>> lpeg = require "lpeg"
>> lpeg.version()
> 1.0.0
>
> Since the problem only occurs intermittently, I run markdown_test.lua as such:
> #!/usr/bin/bash -e
> while true; do
>   ./markdown_test.lua
> done
>
> Looking at the core dump, I see:
>
> #0  0x00007f3fb7060889 in hascaptures (tree=0x0) at lpcode.c:131
> #1  0x00007f3fb706092c in hascaptures (tree=0x56012245c45c) at lpcode.c:144
> #2  0x00007f3fb706092c in hascaptures (tree=0x56012245c454) at lpcode.c:144
> #3  0x00007f3fb706092c in hascaptures (tree=0x56012245c1dc) at lpcode.c:144
> #4  0x00007f3fb706092c in hascaptures (tree=0x56012245c46c) at lpcode.c:144
> #5  0x00007f3fb706092c in hascaptures (tree=0x56012245c454) at lpcode.c:144
> #6  0x00007f3fb706092c in hascaptures (tree=0x56012245c1dc) at lpcode.c:144
> #7  0x00007f3fb706092c in hascaptures (tree=0x56012245c46c) at lpcode.c:144
> #8  0x00007f3fb706092c in hascaptures (tree=0x56012245c454) at lpcode.c:144
> #9  0x00007f3fb706092c in hascaptures (tree=0x56012245c1dc) at lpcode.c:144
> #10 0x00007f3fb706092c in hascaptures (tree=0x56012245c46c) at lpcode.c:144
> #11 0x00007f3fb706092c in hascaptures (tree=0x56012245c454) at lpcode.c:144
> #12 0x00007f3fb706092c in hascaptures (tree=0x56012245c1dc) at lpcode.c:144
> #13 0x00007f3fb706092c in hascaptures (tree=0x56012245c46c) at lpcode.c:144
> #14 0x00007f3fb706092c in hascaptures (tree=0x56012245c454) at lpcode.c:144
> #15 0x00007f3fb706092c in hascaptures (tree=0x56012245c1dc) at lpcode.c:144
> #16 0x00007f3fb706092c in hascaptures (tree=0x56012245c46c) at lpcode.c:144
> #17 0x00007f3fb706092c in hascaptures (tree=0x56012245c454) at lpcode.c:144
> #18 0x00007f3fb706092c in hascaptures (tree=0x56012245c1dc) at lpcode.c:144
> #19 0x00007f3fb706092c in hascaptures (tree=0x56012245c46c) at lpcode.c:144
> #20 0x00007f3fb706092c in hascaptures (tree=0x56012245c454) at lpcode.c:144
> #21 0x00007f3fb706092c in hascaptures (tree=0x56012245c1dc) at lpcode.c:144
> #22 0x00007f3fb706092c in hascaptures (tree=0x56012245c46c) at lpcode.c:144
> #23 0x00007f3fb706092c in hascaptures (tree=0x56012245c454) at lpcode.c:144
> #24 0x00007f3fb706092c in hascaptures (tree=0x56012245c1dc) at lpcode.c:144
> #25 0x00007f3fb706092c in hascaptures (tree=0x56012245c46c) at lpcode.c:144
> #26 0x00007f3fb706092c in hascaptures (tree=0x56012245c454) at lpcode.c:144
>
> [...]
>
> #261630 0x00007f3fb706092c in hascaptures (tree=0x56012245c1dc) at lpcode.c:144
> #261631 0x00007f3fb706092c in hascaptures (tree=0x56012245c18c) at lpcode.c:144
> #261632 0x00007f3fb706092c in hascaptures (tree=0x56012245c10c) at lpcode.c:144
> #261633 0x00007f3fb706092c in hascaptures (tree=0x56012245c674) at lpcode.c:144
> #261634 0x00007f3fb7061c6e in codecapture (compst=0x7ffef2f91360,
> tree=0x56012245c66c, tt=-1, fl=0x7ffef2f901a0) at lpcode.c:720
> #261635 0x00007f3fb706266a in codegen (compst=0x7ffef2f91360,
> tree=0x56012245c66c, opt=0, tt=-1, fl=0x7ffef2f901a0) at lpcode.c:905
> #261636 0x00007f3fb7061af1 in codechoice (compst=0x7ffef2f91360,
> p1=0x56012245c664, p2=0x56012245c66c, opt=0, fl=0x7ffef2f901a0) at
> lpcode.c:682
> #261637 0x00007f3fb70625db in codegen (compst=0x7ffef2f91360,
> tree=0x56012245c65c, opt=0, tt=-1, fl=0x7ffef2f901a0) at lpcode.c:900
> #261638 0x00007f3fb7062491 in codeseq1 (compst=0x7ffef2f91360,
> p1=0x56012245c65c, p2=0x56012245c694, tt=-1, fl=0x7f3fb7063d40
> <fullset_>) at lpcode.c:876
> #261639 0x00007f3fb70626f3 in codegen (compst=0x7ffef2f91360,
> tree=0x56012245c654, opt=0, tt=-1, fl=0x7f3fb7063d40 <fullset_>) at
> lpcode.c:910
> #261640 0x00007f3fb7061d18 in codecapture (compst=0x7ffef2f91360,
> tree=0x56012245c64c, tt=-1, fl=0x7f3fb7063d40 <fullset_>) at
> lpcode.c:726
> #261641 0x00007f3fb706266a in codegen (compst=0x7ffef2f91360,
> tree=0x56012245c64c, opt=0, tt=-1, fl=0x7f3fb7063d40 <fullset_>) at
> lpcode.c:905
> #261642 0x00007f3fb7061da0 in coderuntime (compst=0x7ffef2f91360,
> tree=0x56012245c644, tt=-1) at lpcode.c:734
> #261643 0x00007f3fb7062685 in codegen (compst=0x7ffef2f91360,
> tree=0x56012245c644, opt=0, tt=-1, fl=0x7f3fb7063d40 <fullset_>) at
> lpcode.c:906
> #261644 0x00007f3fb70622f6 in codegrammar (compst=0x7ffef2f91360,
> grammar=0x56012245c02c) at lpcode.c:850
> #261645 0x00007f3fb706269d in codegen (compst=0x7ffef2f91360,
> tree=0x56012245c02c, opt=0, tt=-1, fl=0x7f3fb7063d40 <fullset_>) at
> lpcode.c:907
> #261646 0x00007f3fb7061d18 in codecapture (compst=0x7ffef2f91360,
> tree=0x56012245c024, tt=-1, fl=0x7f3fb7063d40 <fullset_>) at
> lpcode.c:726
> #261647 0x00007f3fb706266a in codegen (compst=0x7ffef2f91360,
> tree=0x56012245c024, opt=0, tt=-1, fl=0x7f3fb7063d40 <fullset_>) at
> lpcode.c:905
> #261648 0x00007f3fb70629b1 in compile (L=0x560122446018,
> p=0x56012245c018) at lpcode.c:977
> #261649 0x00007f3fb705fd7d in prepcompile (L=0x560122446018,
> p=0x56012245c018, idx=1) at lptree.c:1099
> #261650 0x00007f3fb705ff7b in lp_match (L=0x560122446018) at lptree.c:1154
> #261651 0x00007f3fb81d97aa in luaD_precall (L=L@entry=0x560122446018,
> func=func@entry=0x560122456170, nresults=nresults@entry=1) at
> ldo.c:365
> #261652 0x00007f3fb81ef5fd in luaV_execute (L=L@entry=0x560122446018)
> at lvm.c:1134
> #261653 0x00007f3fb81d9b9f in luaD_call (L=L@entry=0x560122446018,
> func=<optimized out>, nResults=<optimized out>) at ldo.c:496
> #261654 0x00007f3fb81d9bf1 in luaD_callnoyield (L=0x560122446018,
> func=<optimized out>, nResults=<optimized out>) at ldo.c:506
> #261655 0x00007f3fb81d8fc2 in luaD_rawrunprotected
> (L=L@entry=0x560122446018, f=f@entry=0x7f3fb81cf250 <f_call>,
> ud=ud@entry=0x7ffef2f918a0) at ldo.c:142
> #261656 0x00007f3fb81d9e7d in luaD_pcall (L=L@entry=0x560122446018,
> func=func@entry=0x7f3fb81cf250 <f_call>, u=u@entry=0x7ffef2f918a0,
> old_top=80, ef=<optimized out>)
>     at ldo.c:727
> #261657 0x00007f3fb81d0851 in lua_pcallk (L=0x560122446018, nargs=0,
> nresults=-1, errfunc=<optimized out>, ctx=0, k=0x0) at lapi.c:968
> #261658 0x0000560121f058ab in docall (L=0x560122446018, narg=0,
> nres=-1) at lua.c:203
> #261659 0x0000560121f0646c in handle_script (argv=<optimized out>,
> L=0x560122446018) at lua.c:443
> #261660 pmain (L=0x560122446018) at lua.c:577
> #261661 0x00007f3fb81d97aa in luaD_precall (L=L@entry=0x560122446018,
> func=0x560122446640, nresults=1) at ldo.c:365
> #261662 0x00007f3fb81d9b93 in luaD_call (L=L@entry=0x560122446018,
> func=<optimized out>, nResults=<optimized out>) at ldo.c:495
> #261663 0x00007f3fb81d9bf1 in luaD_callnoyield (L=0x560122446018,
> func=<optimized out>, nResults=<optimized out>) at ldo.c:506
> #261664 0x00007f3fb81d8fc2 in luaD_rawrunprotected
> (L=L@entry=0x560122446018, f=f@entry=0x7f3fb81cf250 <f_call>,
> ud=ud@entry=0x7ffef2f91b40) at ldo.c:142
> #261665 0x00007f3fb81d9e7d in luaD_pcall (L=L@entry=0x560122446018,
> func=func@entry=0x7f3fb81cf250 <f_call>, u=u@entry=0x7ffef2f91b40,
> old_top=16, ef=<optimized out>)
>     at ldo.c:727
> #261666 0x00007f3fb81d0851 in lua_pcallk (L=0x560122446018, nargs=2,
> nresults=1, errfunc=<optimized out>, ctx=0, k=0x0) at lapi.c:968
> #261667 0x0000560121f0565b in main (argc=2, argv=0x7ffef2f91c88) at lua.c:603
>
> I'm not familiar enough with LPeg or PEG in general to know what's
> causing the crash. Any ideas?
>
> Again, sorry for sending a partial e-mail earlier.
>
> //Sebastian Cato
>
> On Sun, Sep 11, 2016 at 6:12 PM, Sebastian Cato <seb.cato@gmail.com> wrote:
>>
>> Hello,
>>
>> I started writing a markdown (or a dialect thereof) to HTML translator to play around with LPeg.
>>