Re: [Tarantool-patches] [PATCH luajit] Prevent snapshot purge while recording a function header.

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

Hi, Sergey!
Thanks for the review!
See my answer below.

On 03.03.26, Sergey Bronnikov wrote:
> Hi, Sergey,
> 
> thanks for the patch! LGTM with a minor comment.
> 
> Sergey
> 
> On 2/25/26 15:11, Sergey Kaplun wrote:

<snipped>

> > +
> > +local checkers = {}
> > +
> > +-- Called twice for the pseudo-type that aliases base Lua type via
> > +-- checkers map.
> > +local function checks(expected_type)
> > +  -- Value expected to be `checks_tab()` or `checks_obj()`
> > +  -- argument. It is always a table.
> > +  local _, value = debug_getlocal(2, 1)
> > +  -- Simple stitching function. Additional arguments are needed to
> > +  -- occupy the corresponding slot.
> 
> It is not clear for me why this corresponding slot is needed.
> 
> The bug can be reproduced without double nil's passed to math_modf().

Not for all builds (i.e. GC64 and non-GC64).

> 
> > +  math_modf(0, nil, nil)
> > +  -- Start trace now, one iteration only.
> > +  -- luacheck: ignore 512
> > +  while true do
> > +    -- Base type?
> > +    if type(value) == expected_type then
> > +      return true
> > +    end
> > +    -- Pseudo types fallbacks to the map.
> > +    local checker = checkers[expected_type]
> > +    -- For the xpcall.
> > +    if checker(value) == true then
> > +      return true
> > +    end
> > +    break
> > +  end
> > +  error('Unreachable path taken')
> > +end

<snipped>

-- 
Best regards,
Sergey Kaplun