Re: [Tarantool-patches] [PATCH] luajit-gdb: fix misalignment in lj-stack

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

Hi!

Thanks for the patch!
LGTM, except several nits to the commit message.

On 30.06.21, Mikhail Shishatskiy wrote:

| luajit-gdb: fix misalignment in lj-stack

Please use just
| gdb: fix misalignment in lj-stack for LJ_GC64
"tag" (you can check all tags types in the git log).

> When LJ_GC64 was enabled, the alignment of stack slots printed by
> lj-stack command failed. It looked like the following:

Nit: I suggest reformulate it like the following:

| When LJ_GC64 is enabled, stack slots printed by lj-stack command
| are misaligned.

> 
> | 0x7ffff7fb0d90:0x7ffff7fb0dc0 [    ] 7 slots: Red zone
> | 0x7ffff7fb0d88            [   M]
> | 0x7ffff7fb0cc0:0x7ffff7fb0d80 [    ] 25 slots: Free stack slots
> | 0x7ffff7fb0cb8            [  T ]

Nit: please describe the reason of this issue

> 
> This patch fixes the output to look as expected:

Nit: by how?

> 
> | 0x7ffff7fb0d90:0x7ffff7fb0dc0 [    ] 7 slots: Red zone
> | 0x7ffff7fb0d88                [   M]
> | 0x7ffff7fb0cc0:0x7ffff7fb0d80 [    ] 25 slots: Free stack slots
> | 0x7ffff7fb0cb8                [  T ]
> 
> To test changes do the following:
> 
> | $ gdb -q --args ./luajit -e 'print("QQ")'
> | Reading symbols from ./luajit...
> | lj-arch command initialized
> | lj-tv command initialized
> | lj-str command initialized
> | lj-tab command initialized
> | lj-stack command initialized
> | lj-state command initialized
> | lj-gc command initialized
> | luajit-gdb.py is successfully loaded
> | (gdb) lj-arch
> | LJ_64: True, LJ_GC64: True
> | (gdb) b lj_cf_print
> | Breakpoint 1 at 0x298b0: file /mnt/WorkDisk/share/dev/__tarantool/lj-tarantool/src/lib_base.c, line 485.
> | (gdb) r
> | Starting program: /mnt/WorkDisk/share/dev/__tarantool/lj-tarantool/src/luajit -e print\(\"QQ\"\)
> |
> | Breakpoint 1, lj_cf_print (L=0x0)
> |     at /mnt/WorkDisk/share/dev/__tarantool/lj-tarantool/src/lib_base.c:485
> | 485	{
> | (gdb) s
> | 486	  ptrdiff_t i, nargs = L->top - L->base;
> | (gdb) lj-stack L
> | 0x7ffff7fa8d90:0x7ffff7fa8dc0 [    ] 7 slots: Red zone
> | 0x7ffff7fa8d88                [   M]
> | 0x7ffff7fa8cc0:0x7ffff7fa8d80 [    ] 25 slots: Free stack slots
> | 0x7ffff7fa8cb8                [  T ]
> | 0x7ffff7fa8cb0                [ B  ] VALUE: string "QQ" @ 0x7ffff7fb1178
> | 0x7ffff7fa8ca0:0x7ffff7fa8ca8 [    ] FRAME: [L] delta=2, fast function #29
> | 0x7ffff7fa8c90:0x7ffff7fa8c98 [    ] FRAME: [V] delta=2, Lua function @ 0x7ffff7fb1240, 0 upvalues, "=(command line)":0
> | 0x7ffff7fa8c80:0x7ffff7fa8c88 [    ] FRAME: [CP] delta=4, Lua function @ 0x7ffff7fb1240, 0 upvalues, "=(command line)":0
> | 0x7ffff7fa8c78                [    ] VALUE: C function @ 0x55555555c962
> | 0x7ffff7fa8c70                [    ] VALUE: light userdata @ 0x0
> | 0x7ffff7fa8c60:0x7ffff7fa8c68 [    ] FRAME: [CP] delta=2, C function @ 0x55555555df1c
> | 0x7ffff7fa8c58:0x7ffff7fa8c60 [S   ] FRAME: dummy L

Thanks for the test case! Please delete it from commit message (it's
redundant there, I suppose). You can mention it in the mail itself after
"---" before the diff entry [*] (see below).

> 
> Fixes: tarantool/tarantool#5876
> 
> Branch: https://github.com/tarantool/luajit/tree/shishqa/gh-5876

This too [*] (especially it is not a part of the commit message).

> 
> ---

<<< [*] Exactly here.

>  src/luajit-gdb.py | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/luajit-gdb.py b/src/luajit-gdb.py
> index f1fd6230..720d989a 100644
> --- a/src/luajit-gdb.py
> +++ b/src/luajit-gdb.py

<snipped>

> -- 
> 2.32.0
> 

-- 
Best regards,
Sergey Kaplun