Re: [Tarantool-patches] [PATCH] gdb: support full-range 64-bit lightuserdata

[Igor Munkin via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Max,

Thanks for the fixes, but the patch doesn't work now. See my comments
below.

On 02.12.22, Maxim Kokryashkin wrote:
> Following up the introduction of full-range 64-bit lightuserdata
> support in commit 2cacfa8e7ffefb715abf55dc5b0c708c63251868 ('Add
> support for full-range 64 bit lightuserdata.'), this patch
> modifies the corresponding dumper behavior for LJ_64 platforms
> in the luajit-gdb extension.
> 
> Resolves tarantool/tarantool#6481
> ---
>  src/luajit-gdb.py | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/src/luajit-gdb.py b/src/luajit-gdb.py
> index 6480d014..e5c94000 100644
> --- a/src/luajit-gdb.py
> +++ b/src/luajit-gdb.py
> @@ -166,6 +166,12 @@ LJ_GCVMASK = ((1 << 47) - 1)
>  LJ_TISNUM = None
>  PADDING = None
>  
> +# These constants are meaningful only for 'LJ_64' mode.
> +LJ_LIGHTUD_BITS_SEG = 8
> +LJ_LIGHTUD_BITS_LO = 47 - LJ_LIGHTUD_BITS_SEG
> +LIGHTUD_SEG_MASK = (1 << LJ_LIGHTUD_BITS_SEG) - 1
> +LIGHTUD_LO_MASK = (1 << LJ_LIGHTUD_BITS_LO) - 1
> +
>  # }}}
>  
>  def itype(o):
> @@ -315,6 +321,18 @@ def frames(L):
>              break
>          framelink = frame_prev(framelink)
>  

This variable is always false at the moment of declaration, so the hack
doesn't work...

> +if LJ_64:
> +    def lightudV(tv):
> +        u = int(tv['u64'])
> +        # lightudseg macro expanded.
> +        seg = (u >> LJ_LIGHTUD_BITS_LO) & LIGHTUD_SEG_MASK
> +        segmap = mref('uint32_t *', G(L(None))['gc']['lightudseg'])
> +        # lightudlo macro expanded.
> +        return (int(segmap[seg]) << 32) | (u & LIGHTUD_LO_MASK)
> +else:
> +    def lightudV(tv):
> +        return gcval(tv['gcr'])
> +

In my previous review I meant something similar to the following:
| import random
|
| LJ_64 = None
|
| def lightudV_segmented():
|     print(LJ_64, "Segmented lightuserdata is used")
|
| def lightudV_raw():
|     print(LJ_64, "Raw lightuserdata is used")
|
| def init():
|     global lightudV, LJ_64
|     LJ_64 = random.randint(0, 1)
|     lightudV = lightudV_segmented if LJ_64 else lightudV_raw
|
| init()
| lightudV()

In other words, you have to choose the implementation of lightudV on
extension initilalization step (when LJ_64 is resolved), not on script
load phase.

>  # Dumpers {{{
>  
>  def dump_lj_tnil(tv):
> @@ -327,7 +345,7 @@ def dump_lj_ttrue(tv):
>      return 'true'
>  
>  def dump_lj_tlightud(tv):
> -    return 'light userdata @ {}'.format(strx64(gcval(tv['gcr'])))
> +    return 'light userdata @ {}'.format(strx64(lightudV(tv)))
>  
>  def dump_lj_tstr(tv):
>      return 'string {body} @ {address}'.format(
> -- 
> 2.38.1
> 

-- 
Best regards,
IM