Re: [Tarantool-patches] [PATCH v2 luajit 3/3] gdb: enhance the extension loading

[Igor Munkin <imun@tarantool.org>]

Damn the old Python:

| (gdb) source ~/luajit-gdb.py
| Traceback (most recent call last):
|   File "~/luajit-gdb.py", line 686, in <module>
|   File "~/luajit-gdb.py", line 675, in load
|   File "~/luajit-gdb.py", line 468, in __init__
| NameError: global name '__class__' is not defined
| (gdb) python
| >import sys
| >print(sys.version)
| >2.7.5 (default, Aug  7 2019, 00:51:29) 
| [GCC 4.8.5 20150623 (Red Hat 4.8.5-39)]

I'll fix the issue and send either diff or a new patch for this one in a
jiffy.

On 05.02.20, Igor Munkin wrote:
> Definition of LJ_64, LJ_GC64 and LJ_FR2 constants in script requires
> LuaJIT internal enum values to be presented in the executable. Otherwise
> the extension loading fails. The changes handles exception for the
> following scenarios:
> * luajit-gdb.py is loaded for an arbitrary executable, e.g. /bin/echo
> * luajit-gdb.py is loaded for a luajit executable (or the one linked
>   against libluajit) but debug info is not found
> 
> Signed-off-by: Igor Munkin <imun@tarantool.org>
> ---
>  src/luajit-gdb.py | 102 ++++++++++++++++++++--------------------------
>  1 file changed, 45 insertions(+), 57 deletions(-)
> 
> diff --git a/src/luajit-gdb.py b/src/luajit-gdb.py
> index 90df101..bc37674 100644
> --- a/src/luajit-gdb.py
> +++ b/src/luajit-gdb.py
> @@ -1,3 +1,6 @@
> +# GDB extension for LuaJIT post-mortem analysis.
> +# To use, just put 'source <path-to-repo>/src/luajit-gdb.py' in gdb.
> +
>  import re
>  import gdb
>  import sys
> @@ -151,11 +154,9 @@ def frame_prev(framelink):
>  
>  # Const {{{
>  
> -LJ_64 = str(gdb.parse_and_eval('IRT_PTR')) == 'IRT_P64'
> -
> -LJ_GC64 = str(gdb.parse_and_eval('IRT_PGC')) == 'IRT_P64'
> -
> -LJ_FR2 = LJ_GC64
> +LJ_64 = None
> +LJ_GC64 = None
> +LJ_FR2 = None
>  
>  LJ_GCVMASK = ((1 << 47) - 1)
>  
> @@ -460,7 +461,14 @@ def dump_gc(g):
>  
>      return '\n'.join(map(lambda s: '\t' + s, stats))
>  
> -class LJDumpArch(gdb.Command):
> +
> +class LJBase(gdb.Command):
> +
> +    def __init__(self, name):
> +        super(__class__, self).__init__(name, gdb.COMMAND_DATA)
> +        gdb.write('{} command initialized\n'.format(name))
> +
> +class LJDumpArch(LJBase):
>      '''
>  lj-arch
>  
> @@ -469,20 +477,13 @@ compile-time flags. These values define the sizes of host and GC
>  pointers respectively.
>      '''
>  
> -    def __init__(self):
> -        super(LJDumpArch, self).__init__(
> -            'lj-arch', gdb.COMMAND_DATA
> -        )
> -
>      def invoke(self, arg, from_tty):
>          gdb.write('LJ_64: {LJ_64}, LJ_GC64: {LJ_GC64}\n'.format(
>              LJ_64 = LJ_64,
>              LJ_GC64 = LJ_GC64
>          ))
>  
> -LJDumpArch()
> -
> -class LJDumpTValue(gdb.Command):
> +class LJDumpTValue(LJBase):
>      '''
>  lj-tv <TValue *>
>  
> @@ -511,18 +512,11 @@ Whether the type of the given address differs from the listed above, then
>  error message occurs.
>      '''
>  
> -    def __init__(self):
> -        super(LJDumpTValue, self).__init__(
> -            'lj-tv', gdb.COMMAND_DATA
> -        )
> -
>      def invoke(self, arg, from_tty):
>          tv = cast('TValue *', parse_arg(arg))
>          gdb.write('{}\n'.format(dump_tvalue(tv)))
>  
> -LJDumpTValue()
> -
> -class LJDumpString(gdb.Command):
> +class LJDumpString(LJBase):
>      '''
>  lj-str <GCstr *>
>  
> @@ -533,11 +527,6 @@ the payload, size in bytes and hash.
>  is replaced with the corresponding error when decoding fails.
>      '''
>  
> -    def __init__(self):
> -        super(LJDumpString, self).__init__(
> -            'lj-str', gdb.COMMAND_DATA
> -        )
> -
>      def invoke(self, arg, from_tty):
>          string = cast('GCstr *', parse_arg(arg))
>          gdb.write("String: {body} [{len} bytes] with hash {hash}\n".format(
> @@ -546,10 +535,7 @@ is replaced with the corresponding error when decoding fails.
>              len = string['len'],
>          ))
>  
> -
> -LJDumpString()
> -
> -class LJDumpTable(gdb.Command):
> +class LJDumpTable(LJBase):
>      '''
>  lj-tab <GCtab *>
>  
> @@ -561,10 +547,6 @@ The command recieves a GCtab adress and dumps the table contents:
>    <hnode ptr>: { <tv> } => { <tv> }; next = <next hnode ptr>
>      '''
>  
> -    def __init__(self):
> -        super(LJDumpTable, self).__init__(
> -            'lj-tab', gdb.COMMAND_DATA)
> -
>      def invoke(self, arg, from_tty):
>          t = cast('GCtab *', parse_arg(arg))
>          array = mref('TValue *', t['array'])
> @@ -598,9 +580,7 @@ The command recieves a GCtab adress and dumps the table contents:
>                  n = mref('struct Node *', node['next'])
>              ))
>  
> -LJDumpTable()
> -
> -class LJDumpStack(gdb.Command):
> +class LJDumpStack(LJBase):
>      '''
>  lj-stack [<lua_State *>]
>  
> @@ -633,16 +613,10 @@ coroutine guest stack:
>  If L is ommited the main coroutine is used.
>      '''
>  
> -    def __init__(self):
> -        super(LJDumpStack, self).__init__(
> -            'lj-stack', gdb.COMMAND_DATA)
> -
>      def invoke(self, arg, from_tty):
>          gdb.write('{}\n'.format(dump_stack(L(parse_arg(arg)))))
>  
> -LJDumpStack()
> -
> -class LJState(gdb.Command):
> +class LJState(LJBase):
>      '''
>  lj-state
>  The command requires no args and dumps current VM and GC states
> @@ -651,10 +625,6 @@ The command requires no args and dumps current VM and GC states
>  * JIT state: <IDLE|ACTIVE|RECORD|START|END|ASM|ERR>
>      '''
>  
> -    def __init__(self):
> -        super(LJState, self).__init__(
> -            'lj-state', gdb.COMMAND_DATA)
> -
>      def invoke(self, arg, from_tty):
>          g = G(L(None))
>          gdb.write('{}\n'.format('\n'.join(
> @@ -665,9 +635,7 @@ The command requires no args and dumps current VM and GC states
>              }.items())
>          )))
>  
> -LJState()
> -
> -class LJGC(gdb.Command):
> +class LJGC(LJBase):
>      '''
>  lj-gc
>  
> @@ -685,10 +653,6 @@ The command requires no args and dumps current GC stats:
>  * weak: <number of weak tables (to be cleared)>
>      '''
>  
> -    def __init__(self):
> -        super(LJGC, self).__init__(
> -            'lj-gc', gdb.COMMAND_DATA)
> -
>      def invoke(self, arg, from_tty):
>          g = G(L(None))
>          gdb.write('GC stats: {state}\n{stats}\n'.format(
> @@ -696,4 +660,28 @@ The command requires no args and dumps current GC stats:
>              stats = dump_gc(g)
>          ))
>  
> -LJGC()
> +def load(commands):
> +    global LJ_64, LJ_GC64, LJ_FR2
> +
> +    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'
> +    except:
> +        gdb.write('luajit-gdb.py failed to load: '
> +                  'no debugging symbols found for libluajit\n')
> +        return
> +
> +    for name, command in commands.items():
> +        command(name)
> +
> +    gdb.write('luajit-gdb.py is successfully loaded\n')
> +
> +load({
> +    'lj-arch': LJDumpArch,
> +    'lj-tv': LJDumpTValue,
> +    'lj-str': LJDumpString,
> +    'lj-tab': LJDumpTable,
> +    'lj-stack': LJDumpStack,
> +    'lj-state': LJState,
> +    'lj-gc': LJGC,
> +})
> -- 
> 2.24.0
> 

-- 
Best regards,
IM