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From: Igor Munkin via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Sergey Bronnikov <estetus@gmail.com>
Cc: max.kokryashkin@gmail.com, tarantool-patches@dev.tarantool.org
Subject: Re: [Tarantool-patches] [PATCH luajit] LJ_GC64: Fix lua_concat().
Date: Thu, 23 Nov 2023 06:31:52 +0000	[thread overview]
Message-ID: <ZV7x2LijXCKihjHw@tarantool.org> (raw)
In-Reply-To: <26636e3dcb8ade3bdc23d9544f9a7e2ffe4322b2.1695711374.git.sergeyb@tarantool.org>

Sergey,

I've checked the patchset into all long-term branches in
tarantool/luajit and bumped a new version in master, release/2.11 and
release/2.10.

On 26.09.23, Sergey Bronnikov via Tarantool-patches wrote:
> From: Sergey Bronnikov <sergeyb@tarantool.org>
> 
> Reported by Mathias Westerdahl.
> 
> (cherry picked from commit 633f265f67f322cbe2c5fd11d3e46d968ac220f7)
> 
> Lua 5.1 Reference Manual [1] defines a function `lua_concat`, that:
> 
> > void lua_concat (lua_State *L, int n);
> >
> > Concatenates the n values at the top of the stack, pops them, and leaves
> > the result at the top.
> 
> Without the patch `lua_concat()` behaved incorrectly with userdata with
> defined `__concat` metamethod. The problem is GC64-specific.
> 
> Assuming we have three literals and a userdata with defined "__concat"
> metamethod on top of the Lua stack:
> 
> 1 [string]
> 2 [string]
> 3 [string]
> 4 [string]
> 5 [userdata] <--- top
> 
> On attempt to concatenate *two* items on top Lua stack, `lua_concat()`
> concatenates *four* items and leaves result at the top:
> 
> 1 [string]
> 2 [string][string][string][userdata] <--- top
> 
> The problem is in incorrect calculation of `n` counter in a loop in
> implementation of function `lua_concat`. Without a fix `n` is equal to 3
> at the end of the first iteration and therefore it goes to the next
> iteration of concatenation. In a fixed implementation of `lua_concat()`
> `n` is equal to 1 at the end of the first loop iteration, decremented in
> a loop postcondition and breaks a loop.
> 
> The patch fixes incorrect behaviour.
> 
> 1. https://www.lua.org/manual/5.1/manual.html
> 
> Sergey Bronnikov:
> * added the description and the test for the problem
> 
> Part of tarantool/tarantool#8825
> ---
> PR: https://github.com/tarantool/tarantool/pull/9176
> Branch: https://github.com/tarantool/luajit/commits/ligurio/lj-881-fix-concat
> Issues:
> 	- https://github.com/LuaJIT/LuaJIT/issues/881
> 	- https://github.com/tarantool/tarantool/issues/8825
> 
>  src/lj_api.c                                  |   2 +-
>  .../lj-881-fix-lua-concat.test.c              | 116 ++++++++++++++++++
>  2 files changed, 117 insertions(+), 1 deletion(-)
>  create mode 100644 test/tarantool-c-tests/lj-881-fix-lua-concat.test.c
> 

<snipped>

> -- 
> 2.34.1
> 

-- 
Best regards,
IM

      parent reply	other threads:[~2023-11-23  6:38 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <cover.1698775628.git.sergeyb@tarantool.org>
2023-09-26  6:56 ` Sergey Bronnikov via Tarantool-patches
2023-09-29  8:24   ` Maxim Kokryashkin via Tarantool-patches
2023-10-03 15:35     ` Sergey Bronnikov via Tarantool-patches
2023-10-04 10:48       ` Maxim Kokryashkin via Tarantool-patches
2023-10-06 13:51         ` Sergey Bronnikov via Tarantool-patches
2023-10-31 18:11   ` [Tarantool-patches] [PATCH luajit 1/2] test: introduce asserts assert_str{_not}_equal Sergey Bronnikov via Tarantool-patches
2023-11-01  7:40     ` Sergey Kaplun via Tarantool-patches
2023-11-01  8:28       ` Igor Munkin via Tarantool-patches
2023-11-10 11:41         ` Sergey Bronnikov via Tarantool-patches
2023-11-14  8:55           ` Sergey Kaplun via Tarantool-patches
2023-11-15  9:32             ` Sergey Bronnikov via Tarantool-patches
2023-11-16  8:02               ` Sergey Kaplun via Tarantool-patches
2023-11-18 16:40                 ` Sergey Bronnikov via Tarantool-patches
2023-11-20  9:28                   ` Sergey Kaplun via Tarantool-patches
2023-11-20 13:19                   ` Igor Munkin via Tarantool-patches
2023-11-10 11:40       ` Sergey Bronnikov via Tarantool-patches
2023-11-23  6:31   ` Igor Munkin via Tarantool-patches [this message]

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