[Tarantool-patches] [PATCH luajit v2] luajit-gdb: support dualnum mode

[Sergey Kaplun]

Hi, Maxim!

Thanks for the fixes!

LGTM, except two nitpicks below.

On 14.08.21, Maxim Kokryashkin wrote:
> luajit-gdb.py displays integers in LJ_DUALNUM mode as nan-s. The
> dumper function produces output thinking of any input value as of a
> double. However, in DUALNUM mode, integers and doubles are stored
> differently, so the `itype` of a float number must be less than
> `LJ_TISNUM`, and the `itype` of an integer must be `LJ_TISNUM`. With
> this fact in mind, we can easily differentiate one from another.
> 
> Closes tarantool/tarantool#6224
> ---
> Changes in v2:
>   - Fixed comments as per review by Sergey
> 
>  src/luajit-gdb.py | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/src/luajit-gdb.py b/src/luajit-gdb.py
> index c50405ad..d4882dd7 100644
> --- a/src/luajit-gdb.py
> +++ b/src/luajit-gdb.py
> @@ -238,8 +238,11 @@ def jit_state(g):
>          0x15: 'ERR',
>      }.get(int(J(g)['state']), 'INVALID')
>  
> +def tvisint(o):
> +    return LJ_DUALNUM and itype(o) == LJ_TISNUM
> +
>  def tvisnumber(o):
> -    return itype(o) <= (0xfffeffff if LJ_64 and not LJ_GC64 else LJ_T['NUMX'])
> +    return itype(o) <= LJ_TISNUM

Strictly saying, it is `<`, because `==` is staying for integer
representation.

>  
>  def tvislightud(o):
>      if LJ_64 and not LJ_GC64:
> @@ -343,7 +346,10 @@ def dump_lj_tudata(tv):
>      return 'userdata @ {}'.format(strx64(gcval(tv['gcr'])))
>  
>  def dump_lj_tnumx(tv):
> -    return 'number {}'.format(cast('double', tv['n']))
> +    if tvisint(tv):
> +        return 'number {}'.format(cast('int32_t', tv['i']))

Nit: Lets change it to 'integer {}', as far as it is an integer value in
the internal LuaJIT representation.

> +    else:
> +        return 'number {}'.format(cast('double', tv['n']))
>  
>  def dump_lj_invalid(tv):
>      return 'not valid type @ {}'.format(strx64(gcval(tv['gcr'])))
> @@ -683,7 +689,7 @@ The command requires no args and dumps current GC stats:
>          ))
>  
>  def init(commands):
> -    global LJ_64, LJ_GC64, LJ_FR2, PADDING
> +    global LJ_64, LJ_GC64, LJ_DUALNUM, LJ_TISNUM, LJ_FR2, PADDING
>  
>      # XXX Fragile: though connecting the callback looks like a crap but it
>      # respects both Python 2 and Python 3 (see #4828).
> @@ -724,6 +730,7 @@ def init(commands):
>      try:
>          LJ_64 = str(gdb.parse_and_eval('IRT_PTR')) == 'IRT_P64'
>          LJ_FR2 = LJ_GC64 = str(gdb.parse_and_eval('IRT_PGC')) == 'IRT_P64'
> +        LJ_DUALNUM = lookup('lj_lib_checknumber') is not None
>      except:
>          gdb.write('luajit-gdb.py failed to load: '
>                    'no debugging symbols found for libluajit\n')
> @@ -733,6 +740,7 @@ def init(commands):
>          command(name)
>  
>      PADDING = ' ' * len(':' + hex((1 << (47 if LJ_GC64 else 32)) - 1))
> +    LJ_TISNUM = 0xfffeffff if LJ_64 and not LJ_GC64 else LJ_T['NUMX']
>  
>      gdb.write('luajit-gdb.py is successfully loaded\n')
>  
> -- 
> 2.32.0
> 

-- 
Best regards,
Sergey Kaplun