Re: [Tarantool-patches] [PATCH luajit] test: adapt test checking reversed function

[Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Hi!

Thanks for the answer!

On 11.10.21, Максим Корякшин wrote:
> 
> Hi! Thanks for the comments. 
>  
> I agree that it is strange to add this test, as long as it does not test
> anything, so I propose to remove it.

May be as an option, but IMO it is better to leave it commented instead,
as a reminder about the problem. Lets wait for the second reviewer here.
I'm OK with both solutions.

>  
> Best regards,
> Maxim Kokryashkin
>  
> > 
> >>Hi, Maxim!
> >>
> >>Thanks for the patch!
> >>
> >>Please consider my comments below.
> >>
> >>On 30.09.21, Maxim Kokryashkin wrote:
> >>> The first fiber in Tarantool has only 512Kb of the stack which is not enough to
> >>> handle such a deep call chain.
> >>> The test is adapted to Tarantool by decreasing the string length.
> >>>
> >>> Closes tarantool/tarantool#5782
> >>> Part of tarantool/tarantool#5845
> >>> Part of tarantool/tarantool#4473
> >>
> >>Looks like it should be 5870 instead 4473. Also, 5845 is already
> >>closed.
> >>
> >>> ---
> >>
> >>Please show the Tarantool branch as well, to show that problem is gone.
> >>
> >>> GitHub branch:  https://github.com/tarantool/luajit/tree/fckxorg/gh-5782-adapt-deep-nest-gsub-PUC-Rio
> >>> Issue:  https://github.com/tarantool/tarantool/issues/5782
> >>>
> >>> test/PUC-Rio-Lua-5.1-tests/pm.lua | 9 ++++-----
> >>> 1 file changed, 4 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/test/PUC-Rio-Lua-5.1-tests/pm.lua b/test/PUC-Rio-Lua-5.1-tests/pm.lua
> >>> index e364ff9d..7da3ef4a 100644
> >>> --- a/test/PUC-Rio-Lua-5.1-tests/pm.lua
> >>> +++ b/test/PUC-Rio-Lua-5.1-tests/pm.lua
> >>> @@ -206,12 +206,11 @@ function rev (s)
> >>> return string.gsub(s, "(.)(.+)", function (c,s1) return rev(s1)..c end)
> >>> end
> >>>
> >>> -local x = string.rep('012345', 10)
> >>> --- FIXME: The first Tarantool's fiber has only 512Kb of stack.
> >>> --- It is not enough for this recursive call.
> >>> +-- This test is adapted to match the stack size (512Kb) of the first fiber in
> >>> +-- Tarantool.
> >>> -- See also  https://github.com/tarantool/tarantool/issues/5782 .
> >>> --- The test is disabled for Tarantool binary.
> >>> --- assert(rev(rev(x)) == x)
> >>> +local x = string.rep('01234', 10)
> >>> +assert(rev(rev(x)) == x)
> >>
> >>The patch is looks OK to me, but the main problem is still here:
> >>LuaJIT is badly managing C stack overflow. The same chunk rases an error
> >>for Lua 5.1, but crashes for LuaJIT.
> >>
> >>| $ luajit -e 'local function rev (s) return string.gsub(s, "(.)(.+)", function (c,s1) return rev(s1)..c end) end local x = string.rep("0", 1000) rev(x)'
> >>| Segmentation fault
> >>
> >>| $ lua -e 'local function rev (s) return string.gsub(s, "(.)(.+)", function (c,s1) return rev(s1)..c end) end local x = string.rep("0", 1000) rev(x)'
> >>| lua: C stack overflow
> >>| stack traceback:
> >>| [C]: in function 'gsub'
> >>| (command line):1: in function 'rev'
> >>| (command line):1: in function <(command line):1>
> >>| [C]: in function 'gsub'
> >>| (command line):1: in function 'rev'
> >>| (command line):1: in function <(command line):1>
> >>| [C]: in function 'gsub'
> >>| (command line):1: in function 'rev'
> >>| (command line):1: in function <(command line):1>
> >>| [C]: in function 'gsub'
> >>| ...
> >>| [C]: in function 'gsub'
> >>| (command line):1: in function 'rev'
> >>| (command line):1: in function <(command line):1>
> >>| [C]: in function 'gsub'
> >>| (command line):1: in function 'rev'
> >>| (command line):1: in function <(command line):1>
> >>| [C]: in function 'gsub'
> >>| (command line):1: in function 'rev'
> >>| (command line):1: in main chunk
> >>| [C]: ?
> >>
> >>So I suppose it is strange to add test that tests nothing.
> >>
> >>Thoughts?
> >>
> >>>
> >>>
> >>> -- gsub with tables
> >>> --
> >>> 2.33.0
> >>>
> >>
> >>--
> >>Best regards,
> >>Sergey Kaplun
> > 

-- 
Best regards,
Sergey Kaplun