Re: [Tarantool-patches] [PATCH luajit v3] dbg: display fast function name along with ffid

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

Hi, Mikhail,

thanks for the patch! LGTM with minor comments below.

Sergey

On 9/24/26 23:14, Mikhail Elhimov wrote:
> Part of tarantool/tarantool#4808
> ---
> Changes in v3:
>    - Fixed fast function regexp in tests
>
> Changes in v2:
>    - Format is changed to 'ffname (#ffid)'
>    - Replaced single '_' with '.' in ffname
>    - Adjusted tests to check mapping
>
> This patch is to be applied after https://lists.tarantool.org/pipermail/tarantool-patches/2026-September/030791.html.
>
> Branch: https://github.com/tarantool/luajit/tree/elhimov/gh-4808-display-fast-function-name
> Related issue: https://github.com/tarantool/tarantool/issues/4808
>
>   src/luajit_dbg.py                             | 19 +++++++++++++------
>   .../debug-extension-tests.py                  |  6 ++++--
>   2 files changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/src/luajit_dbg.py b/src/luajit_dbg.py
> index 5cd23a88..a564801b 100644
> --- a/src/luajit_dbg.py
> +++ b/src/luajit_dbg.py
> @@ -1121,6 +1121,11 @@ def frames(L):
>   # LuaJIT macro implementations and structure access.
>   
>   
> +# Get FastFunc enum members and replace any single '_' with '.'.
> +FF_NAMES = EnumBasedList('FastFunc', 'FF__MAX', lambda x:
> +                         re.sub('(?<!_)_(?!_)', '.', cut_prefix(x, 'FF_')))
> +
> +
>   def mref(typename, obj):
>       return dbg.cast(typename, obj['ptr64'] if LJ_GC64 else obj['ptr32'])
>   
> @@ -1716,7 +1721,7 @@ def dump_lj_gco_proto(gcobj):
>   
>   def dump_lj_gco_func(gcobj):
>       func = dbg.cast('struct GCfuncC *', gcobj)
> -    ffid = func['ffid']
> +    ffid = int(func['ffid'])
>   
>       if ffid == 0:
>           pt = funcproto(func)
> @@ -1729,7 +1734,8 @@ def dump_lj_gco_func(gcobj):
>       elif ffid == 1:
>           return 'C function @ {}'.format(strx64(func['f']))
>       else:
> -        return 'fast function #{}'.format(int(ffid))
> +        ffname = FF_NAMES[ffid] if ffid < len(FF_NAMES) else "unknown"
use single quotes
> +        return 'fast function {} (#{})'.format(ffname, ffid)
>   
>   
>   def dump_lj_gco_trace(gcobj):
> @@ -2079,7 +2085,7 @@ def dump_proto(proto):
>   
>   
>   def dump_func(func):
> -    ffid = func['ffid']
> +    ffid = int(func['ffid'])
>   
>       if ffid == 0:
>           pt = funcproto(func)
> @@ -2087,7 +2093,8 @@ def dump_func(func):
>       elif ffid == 1:
>           return 'C function @ {}\n'.format(strx64(func['f']))
>       else:
> -        return 'fast function #{}\n'.format(int(ffid))
> +        ffname = FF_NAMES[ffid] if ffid < len(FF_NAMES) else "unknown"
the same is used in dump_lj_gco_func(), I would create a helper for this
> +        return 'fast function {} (#{})\n'.format(ffname, ffid)
>   
>   
>   # FFI dumpers.
> @@ -2713,7 +2720,7 @@ the type and some info related to it.
>   * LJ_TFUNC: <LFUNC|CFUNC|FFUNC>
>     <LFUNC>: Lua function @ <gcr>, <nupvals> upvalues, <chunk:line>
>     <CFUNC>: C function <mcode address>
> -  <FFUNC>: fast function #<ffid>
> +  <FFUNC>: fast function <ffname> (#<ffid>)
>   * LJ_TTRACE: trace <traceno> @ <gcr>
>   * LJ_TCDATA: cdata @ <gcr>
>   * LJ_TTAB: table @ <gcr> (asize: <asize>, hmask: <hmask>)
> @@ -2932,7 +2939,7 @@ the type and some info related to it.
>   * LJ_TFUNC: <LFUNC|CFUNC|FFUNC>
>     <LFUNC>: Lua function @ <gcr>, <nupvals> upvalues, <chunk:line>
>     <CFUNC>: C function <mcode address>
> -  <FFUNC>: fast function #<ffid>
> +  <FFUNC>: fast function <ffname> (#<ffid>)
>   * LJ_TTRACE: trace <traceno> @ <gcr>
>   * LJ_TCDATA: cdata @ <gcr>
>   * LJ_TTAB: table @ <gcr> (asize: <asize>, hmask: <hmask>)
> diff --git a/test/tarantool-debugger-tests/debug-extension-tests.py b/test/tarantool-debugger-tests/debug-extension-tests.py
> index 5e369f00..fe5e34f5 100644
> --- a/test/tarantool-debugger-tests/debug-extension-tests.py
> +++ b/test/tarantool-debugger-tests/debug-extension-tests.py
fallback "unknown" is not covered
> @@ -326,7 +326,7 @@ GCO_ARGS = (
>       'coroutine.create(function() end),\n'
>       'function() end,\n'
>       'require,\n'
> -    'print,\n'
> +    'math.min,\n'
>       'ffi.new("int*"),\n'
>       '{1},\n'
>       'newproxy(),\n'
added also tests for: getmetatable(io.stdout).__gc and 
getmetatable(io.stdout).__tostring to cover regexp
> @@ -338,7 +338,7 @@ GCO_RX = (
>       r'thread @ ' + RX_ADDR + r'\n'
>       r'Lua function @ ' + RX_ADDR + r', [0-9]+ upvalues, .+:[0-9]+\n'
>       r'C function @ ' + RX_ADDR + r'\n'
> -    r'fast function #[0-9]+\n'
> +    r'fast function math.min \(#[0-9]+\)\n'
>       r'cdata @ ' + RX_ADDR + r' \[\d+\] <int \*> 0x0\n'
>       r'table @ ' + RX_ADDR + r' \(asize: \d+, hmask: ' + RX_HASH + r'\)\n'
>       r'userdata @ ' + RX_ADDR + r'\n'
> @@ -367,6 +367,7 @@ class TestLJTV(TestCaseBase):
>       # Sorted in LJT order.
>       lua_script = (
>           'local ffi = require("ffi")\n'
> +        'local math = require("math")\n'
>           'print(\n'
>           '  nil,\n'
>           '  false,\n'
> @@ -435,6 +436,7 @@ class TestLJGCo(TestCaseBase):
>   
>       lua_script = (
>           'local ffi = require("ffi")\n'
> +        'local math = require("math")\n'
>           'print(\n' +
>           GCO_ARGS +
>           '  1\n'  # Stub for the pattern.
add also a test with "lj-func" for any ffunc