Re: [Tarantool-patches] [PATCH luajit] Fix overflow check in unpack().

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

Hi, Maxim!

Thanks for the review!

On 06.09.22, Maxim Kokryashkin wrote:
> 
> Hi, Sergey!
> Thanks for the patch!
> Please consider my comments below:
>   
> >from Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org>:
> > 
> >From: Mike Pall <mike>
> >
> >Thanks to HybridDog.
> >
> >When build with optimization compiler may throw away overflow check in
> >`unpack()` base library function.
> Typo: s/build with optimization/built with optimization,
> Also,  I think we should mention the specific optimization that causes the mentioned behavior
> since it is not mentioned in both the LuaJIT’s issue and the original Lua issue.

Fixed.
The new commit message is the following:
I mention the -fstrict-overflow flag as the crucial one (obviously
some more are needed).

| Fix overflow check in unpack().
|
| Thanks to HybridDog.
|
| (cherry picked from commit 179cf2eb84fef2b9a524469c3c8cc49363b8fb10)
|
| When built with -O2 optimization flag (includes -fstrict-overflow)
| compiler throws away overflow check in `unpack()` base library function.
|
| This patch prevents aforementioned error by comparing the unsigned
| amount of values to unpack with `LUAI_MAXCSTACK` instead of 0.
|
| Sergey Kaplun:
| * added the description and the test for the problem
|
| Part of tarantool/tarantool#7230

Branch is force-pushed.

> >
> >This patch prevents aforementioned error by comparing the unsigned
> >amount of values to unpack with `LUAI_MAXCSTACK` instead of 0.
> >
> >Sergey Kaplun:
> >* added the description and the test for the problem
> >
> >Part of tarantool/tarantool#7230
> >---
> >
> >Issue/PR:
> >*  https://github.com/LuaJIT/LuaJIT/pull/574
> >*  https://github.com/tarantool/tarantool/issues/7230
> >Branch:  https://github.com/tarantool/luajit/tree/skaplun/lj-574-overflow-unpack-full-ci
> >PR:  https://github.com/tarantool/tarantool/pull/7596
> >
> > src/lib_base.c | 6 ++++--
> > test/tarantool-tests/lj-574-overflow-unpack.test.lua | 12 ++++++++++++

<snipped>

> >--
> >2.34.1
> --
> Best regards,
> Maxim Kokryashkin

-- 
Best regards,
Sergey Kaplun