Re: [Tarantool-patches] [PATCH luajit v6 1/2] debug: generalized extension

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

Hi, Max


LGTM, as I said for a previous version.


On 4/4/24 01:21, Maxim Kokryashkin wrote:
> This patch joins the LLDB and GDB LuaJIT debugging extensions
> into one, so now the extension logic can be debugger-agnostic.
> To do that, an adapter class is introduced, and all of the
> debugger-specific behavior is encapsulated there. The extension
> auto-detects the debugger it was loaded into and selects the
> correct low-level logic implementation.
> ---
>   src/luajit-gdb.py                     | 885 --------------------------
>   src/{luajit_lldb.py => luajit_dbg.py} | 616 ++++++++++++------
>   2 files changed, 416 insertions(+), 1085 deletions(-)
>   delete mode 100644 src/luajit-gdb.py
>   rename src/{luajit_lldb.py => luajit_dbg.py} (63%)
>
> diff --git a/src/luajit-gdb.py b/src/luajit-gdb.py
> deleted file mode 100644
> index d2070e9b..00000000
> --- a/src/luajit-gdb.py
> +++ /dev/null
> @@ -1,885 +0,0 @@
> -# 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
> -
> -# make script compatible with the ancient Python {{{
> -
> -
> -LEGACY = re.match(r'^2\.', sys.version)
> -
> -if LEGACY:
> -    CONNECTED = False
> -    int = long
> -    range = xrange
> -
> -
> -# }}}
> -
> -
> -gtype_cache = {}
> -
> -
> -def gtype(typestr):
> -    global gtype_cache
> -    if typestr in gtype_cache:
> -        return gtype_cache[typestr]
> -
> -    m = re.match(r'((?:(?:struct|union) )?\S*)\s*[*]', typestr)
> -
> -    gtype = gdb.lookup_type(typestr) if m is None \
> -        else gdb.lookup_type(m.group(1)).pointer()
> -
> -    gtype_cache[typestr] = gtype
> -    return gtype
> -
> -
> -def cast(typestr, val):
> -    return gdb.Value(val).cast(gtype(typestr))
> -
> -
> -def lookup(symbol):
> -    variable, _ = gdb.lookup_symbol(symbol)
> -    return variable.value() if variable else None
> -
> -
> -def parse_arg(arg):
> -    if not arg:
> -        return None
> -
> -    ret = gdb.parse_and_eval(arg)
> -
> -    if not ret:
> -        raise gdb.GdbError('table argument empty')
> -
> -    return ret
> -
> -
> -def tou64(val):
> -    return cast('uint64_t', val) & 0xFFFFFFFFFFFFFFFF
> -
> -
> -def tou32(val):
> -    return cast('uint32_t', val) & 0xFFFFFFFF
> -
> -
> -def i2notu32(val):
> -    return ~int(val) & 0xFFFFFFFF
> -
> -
> -def strx64(val):
> -    return re.sub('L?$', '',
> -                  hex(int(cast('uint64_t', val) & 0xFFFFFFFFFFFFFFFF)))
> -
> -
> -# Types {{{
> -
> -
> -LJ_T = {
> -    'NIL':     i2notu32(0),
> -    'FALSE':   i2notu32(1),
> -    'TRUE':    i2notu32(2),
> -    'LIGHTUD': i2notu32(3),
> -    'STR':     i2notu32(4),
> -    'UPVAL':   i2notu32(5),
> -    'THREAD':  i2notu32(6),
> -    'PROTO':   i2notu32(7),
> -    'FUNC':    i2notu32(8),
> -    'TRACE':   i2notu32(9),
> -    'CDATA':   i2notu32(10),
> -    'TAB':     i2notu32(11),
> -    'UDATA':   i2notu32(12),
> -    'NUMX':    i2notu32(13),
> -}
> -
> -
> -def typenames(value):
> -    return {
> -        LJ_T[k]: 'LJ_T' + k for k in LJ_T.keys()
> -    }.get(int(value), 'LJ_TINVALID')
> -
> -
> -# }}}
> -
> -# Frames {{{
> -
> -
> -FRAME_TYPE = 0x3
> -FRAME_P = 0x4
> -FRAME_TYPEP = FRAME_TYPE | FRAME_P
> -
> -FRAME = {
> -    'LUA':    0x0,
> -    'C':      0x1,
> -    'CONT':   0x2,
> -    'VARG':   0x3,
> -    'LUAP':   0x4,
> -    'CP':     0x5,
> -    'PCALL':  0x6,
> -    'PCALLH': 0x7,
> -}
> -
> -
> -def frametypes(ft):
> -    return {
> -        FRAME['LUA']:  'L',
> -        FRAME['C']:    'C',
> -        FRAME['CONT']: 'M',
> -        FRAME['VARG']: 'V',
> -    }.get(ft, '?')
> -
> -
> -def bc_a(ins):
> -    return (ins >> 8) & 0xff
> -
> -
> -def frame_ftsz(framelink):
> -    return cast('ptrdiff_t', framelink['ftsz'] if LJ_FR2
> -                else framelink['fr']['tp']['ftsz'])
> -
> -
> -def frame_pc(framelink):
> -    return cast('BCIns *', frame_ftsz(framelink)) if LJ_FR2 \
> -        else mref('BCIns *', framelink['fr']['tp']['pcr'])
> -
> -
> -def frame_prevl(framelink):
> -    return framelink - (1 + LJ_FR2 + bc_a(frame_pc(framelink)[-1]))
> -
> -
> -def frame_ispcall(framelink):
> -    return (frame_ftsz(framelink) & FRAME['PCALL']) == FRAME['PCALL']
> -
> -
> -def frame_sized(framelink):
> -    return (frame_ftsz(framelink) & ~FRAME_TYPEP)
> -
> -
> -def frame_prevd(framelink):
> -    return cast('TValue *', cast('char *', framelink) - frame_sized(framelink))
> -
> -
> -def frame_type(framelink):
> -    return frame_ftsz(framelink) & FRAME_TYPE
> -
> -
> -def frame_typep(framelink):
> -    return frame_ftsz(framelink) & FRAME_TYPEP
> -
> -
> -def frame_islua(framelink):
> -    return frametypes(int(frame_type(framelink))) == 'L' \
> -        and int(frame_ftsz(framelink)) > 0
> -
> -
> -def frame_prev(framelink):
> -    return frame_prevl(framelink) if frame_islua(framelink) \
> -        else frame_prevd(framelink)
> -
> -
> -def frame_sentinel(L):
> -    return mref('TValue *', L['stack']) + LJ_FR2
> -
> -
> -# }}}
> -
> -# Const {{{
> -
> -
> -LJ_64 = None
> -LJ_GC64 = None
> -LJ_FR2 = None
> -LJ_DUALNUM = None
> -
> -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):
> -    return cast('uint32_t', o['it64'] >> 47) if LJ_GC64 else o['it']
> -
> -
> -def mref(typename, obj):
> -    return cast(typename, obj['ptr64'] if LJ_GC64 else obj['ptr32'])
> -
> -
> -def gcref(obj):
> -    return cast('GCobj *', obj['gcptr64'] if LJ_GC64
> -                else cast('uintptr_t', obj['gcptr32']))
> -
> -
> -def gcval(obj):
> -    return cast('GCobj *', obj['gcptr64'] & LJ_GCVMASK if LJ_GC64
> -                else cast('uintptr_t', obj['gcptr32']))
> -
> -
> -def gcnext(obj):
> -    return gcref(obj)['gch']['nextgc']
> -
> -
> -def L(L=None):
> -    # lookup a symbol for the main coroutine considering the host app
> -    # XXX Fragile: though the loop initialization looks like a crap but it
> -    # respects both Python 2 and Python 3.
> -    for lstate in [L] + list(map(lambda main: lookup(main), (
> -        # LuaJIT main coro (see luajit/src/luajit.c)
> -        'globalL',
> -        # Tarantool main coro (see tarantool/src/lua/init.h)
> -        'tarantool_L',
> -        # TODO: Add more
> -    ))):
> -        if lstate:
> -            return cast('lua_State *', lstate)
> -
> -
> -def G(L):
> -    return mref('global_State *', L['glref'])
> -
> -
> -def J(g):
> -    typeGG = gtype('GG_State')
> -
> -    return cast('jit_State *', int(cast('char *', g))
> -                - int(typeGG['g'].bitpos / 8)
> -                + int(typeGG['J'].bitpos / 8))
> -
> -
> -def vm_state(g):
> -    return {
> -        i2notu32(0): 'INTERP',
> -        i2notu32(1): 'LFUNC',
> -        i2notu32(2): 'FFUNC',
> -        i2notu32(3): 'CFUNC',
> -        i2notu32(4): 'GC',
> -        i2notu32(5): 'EXIT',
> -        i2notu32(6): 'RECORD',
> -        i2notu32(7): 'OPT',
> -        i2notu32(8): 'ASM',
> -    }.get(int(tou32(g['vmstate'])), 'TRACE')
> -
> -
> -def gc_state(g):
> -    return {
> -        0: 'PAUSE',
> -        1: 'PROPAGATE',
> -        2: 'ATOMIC',
> -        3: 'SWEEPSTRING',
> -        4: 'SWEEP',
> -        5: 'FINALIZE',
> -        6: 'LAST',
> -    }.get(int(g['gc']['state']), 'INVALID')
> -
> -
> -def jit_state(g):
> -    return {
> -        0:    'IDLE',
> -        0x10: 'ACTIVE',
> -        0x11: 'RECORD',
> -        0x12: 'START',
> -        0x13: 'END',
> -        0x14: 'ASM',
> -        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) <= LJ_TISNUM
> -
> -
> -def tvislightud(o):
> -    if LJ_64 and not LJ_GC64:
> -        return (cast('int32_t', itype(o)) >> 15) == -2
> -    else:
> -        return itype(o) == LJ_T['LIGHTUD']
> -
> -
> -def strdata(obj):
> -    # String is printed with pointer to it, thanks to gdb. Just strip it.
> -    try:
> -        return str(cast('char *', cast('GCstr *', obj) + 1))[len(PADDING):]
> -    except UnicodeEncodeError:
> -        return "<luajit-gdb: error occurred while rendering non-ascii slot>"
> -
> -
> -def itypemap(o):
> -    if LJ_64 and not LJ_GC64:
> -        return LJ_T['NUMX'] if tvisnumber(o)       \
> -            else LJ_T['LIGHTUD'] if tvislightud(o) \
> -            else itype(o)
> -    else:
> -        return LJ_T['NUMX'] if tvisnumber(o) else itype(o)
> -
> -
> -def funcproto(func):
> -    assert func['ffid'] == 0
> -
> -    return cast('GCproto *',
> -                mref('char *', func['pc']) - gdb.lookup_type('GCproto').sizeof)
> -
> -
> -def gclistlen(root, end=0x0):
> -    count = 0
> -    while (gcref(root) != end):
> -        count += 1
> -        root = gcnext(root)
> -    return count
> -
> -
> -def gcringlen(root):
> -    if not gcref(root):
> -        return 0
> -    elif gcref(root) == gcref(gcnext(root)):
> -        return 1
> -    else:
> -        return 1 + gclistlen(gcnext(root), gcref(root))
> -
> -
> -gclen = {
> -    'root':      gclistlen,
> -    'gray':      gclistlen,
> -    'grayagain': gclistlen,
> -    'weak':      gclistlen,
> -    # XXX: gc.mmudata is a ring-list.
> -    'mmudata':   gcringlen,
> -}
> -
> -
> -# The generator that implements frame iterator.
> -# Every frame is represented as a tuple of framelink and frametop.
> -def frames(L):
> -    frametop = L['top']
> -    framelink = L['base'] - 1
> -    framelink_sentinel = frame_sentinel(L)
> -    while True:
> -        yield framelink, frametop
> -        frametop = framelink - (1 + LJ_FR2)
> -        if framelink <= framelink_sentinel:
> -            break
> -        framelink = frame_prev(framelink)
> -
> -
> -def lightudV(tv):
> -    if LJ_64:
> -        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:
> -        return gcval(tv['gcr'])
> -
> -
> -# Dumpers {{{
> -
> -
> -def dump_lj_tnil(tv):
> -    return 'nil'
> -
> -
> -def dump_lj_tfalse(tv):
> -    return 'false'
> -
> -
> -def dump_lj_ttrue(tv):
> -    return 'true'
> -
> -
> -def dump_lj_tlightud(tv):
> -    return 'light userdata @ {}'.format(strx64(lightudV(tv)))
> -
> -
> -def dump_lj_tstr(tv):
> -    return 'string {body} @ {address}'.format(
> -        body=strdata(gcval(tv['gcr'])),
> -        address=strx64(gcval(tv['gcr']))
> -    )
> -
> -
> -def dump_lj_tupval(tv):
> -    return 'upvalue @ {}'.format(strx64(gcval(tv['gcr'])))
> -
> -
> -def dump_lj_tthread(tv):
> -    return 'thread @ {}'.format(strx64(gcval(tv['gcr'])))
> -
> -
> -def dump_lj_tproto(tv):
> -    return 'proto @ {}'.format(strx64(gcval(tv['gcr'])))
> -
> -
> -def dump_lj_tfunc(tv):
> -    func = cast('struct GCfuncC *', gcval(tv['gcr']))
> -    ffid = func['ffid']
> -
> -    if ffid == 0:
> -        pt = funcproto(func)
> -        return 'Lua function @ {addr}, {nups} upvalues, {chunk}:{line}'.format(
> -            addr=strx64(func),
> -            nups=int(func['nupvalues']),
> -            chunk=strdata(cast('GCstr *', gcval(pt['chunkname']))),
> -            line=pt['firstline']
> -        )
> -    elif ffid == 1:
> -        return 'C function @ {}'.format(strx64(func['f']))
> -    else:
> -        return 'fast function #{}'.format(int(ffid))
> -
> -
> -def dump_lj_ttrace(tv):
> -    trace = cast('struct GCtrace *', gcval(tv['gcr']))
> -    return 'trace {traceno} @ {addr}'.format(
> -        traceno=strx64(trace['traceno']),
> -        addr=strx64(trace)
> -    )
> -
> -
> -def dump_lj_tcdata(tv):
> -    return 'cdata @ {}'.format(strx64(gcval(tv['gcr'])))
> -
> -
> -def dump_lj_ttab(tv):
> -    table = cast('GCtab *', gcval(tv['gcr']))
> -    return 'table @ {gcr} (asize: {asize}, hmask: {hmask})'.format(
> -        gcr=strx64(table),
> -        asize=table['asize'],
> -        hmask=strx64(table['hmask']),
> -    )
> -
> -
> -def dump_lj_tudata(tv):
> -    return 'userdata @ {}'.format(strx64(gcval(tv['gcr'])))
> -
> -
> -def dump_lj_tnumx(tv):
> -    if tvisint(tv):
> -        return 'integer {}'.format(cast('int32_t', tv['i']))
> -    else:
> -        return 'number {}'.format(cast('double', tv['n']))
> -
> -
> -def dump_lj_invalid(tv):
> -    return 'not valid type @ {}'.format(strx64(gcval(tv['gcr'])))
> -
> -
> -# }}}
> -
> -
> -dumpers = {
> -    'LJ_TNIL':     dump_lj_tnil,
> -    'LJ_TFALSE':   dump_lj_tfalse,
> -    'LJ_TTRUE':    dump_lj_ttrue,
> -    'LJ_TLIGHTUD': dump_lj_tlightud,
> -    'LJ_TSTR':     dump_lj_tstr,
> -    'LJ_TUPVAL':   dump_lj_tupval,
> -    'LJ_TTHREAD':  dump_lj_tthread,
> -    'LJ_TPROTO':   dump_lj_tproto,
> -    'LJ_TFUNC':    dump_lj_tfunc,
> -    'LJ_TTRACE':   dump_lj_ttrace,
> -    'LJ_TCDATA':   dump_lj_tcdata,
> -    'LJ_TTAB':     dump_lj_ttab,
> -    'LJ_TUDATA':   dump_lj_tudata,
> -    'LJ_TNUMX':    dump_lj_tnumx,
> -}
> -
> -
> -def dump_tvalue(tvalue):
> -    return dumpers.get(typenames(itypemap(tvalue)), dump_lj_invalid)(tvalue)
> -
> -
> -def dump_framelink_slot_address(fr):
> -    return '{}:{}'.format(fr - 1, fr) if LJ_FR2 \
> -        else '{}'.format(fr) + PADDING
> -
> -
> -def dump_framelink(L, fr):
> -    if fr == frame_sentinel(L):
> -        return '{addr} [S   ] FRAME: dummy L'.format(
> -            addr=dump_framelink_slot_address(fr),
> -        )
> -    return '{addr} [    ] FRAME: [{pp}] delta={d}, {f}'.format(
> -        addr=dump_framelink_slot_address(fr),
> -        pp='PP' if frame_ispcall(fr) else '{frname}{p}'.format(
> -            frname=frametypes(int(frame_type(fr))),
> -            p='P' if frame_typep(fr) & FRAME_P else ''
> -        ),
> -        d=cast('TValue *', fr) - cast('TValue *', frame_prev(fr)),
> -        f=dump_lj_tfunc(fr - LJ_FR2),
> -    )
> -
> -
> -def dump_stack_slot(L, slot, base=None, top=None):
> -    base = base or L['base']
> -    top = top or L['top']
> -
> -    return '{addr}{padding} [ {B}{T}{M}] VALUE: {value}'.format(
> -        addr=strx64(slot),
> -        padding=PADDING,
> -        B='B' if slot == base else ' ',
> -        T='T' if slot == top else ' ',
> -        M='M' if slot == mref('TValue *', L['maxstack']) else ' ',
> -        value=dump_tvalue(slot),
> -    )
> -
> -
> -def dump_stack(L, base=None, top=None):
> -    base = base or L['base']
> -    top = top or L['top']
> -    stack = mref('TValue *', L['stack'])
> -    maxstack = mref('TValue *', L['maxstack'])
> -    red = 5 + 2 * LJ_FR2
> -
> -    dump = [
> -        '{padding} Red zone: {nredslots: >2} slots {padding}'.format(
> -            padding='-' * len(PADDING),
> -            nredslots=red,
> -        ),
> -    ]
> -    dump.extend([
> -        dump_stack_slot(L, maxstack + offset, base, top)
> -            for offset in range(red, 0, -1)  # noqa: E131
> -    ])
> -    dump.extend([
> -        '{padding} Stack: {nstackslots: >5} slots {padding}'.format(
> -            padding='-' * len(PADDING),
> -            nstackslots=int((tou64(maxstack) - tou64(stack)) >> 3),
> -        ),
> -        dump_stack_slot(L, maxstack, base, top),
> -        '{start}:{end} [    ] {nfreeslots} slots: Free stack slots'.format(
> -            start=strx64(top + 1),
> -            end=strx64(maxstack - 1),
> -            nfreeslots=int((tou64(maxstack) - tou64(top) - 8) >> 3),
> -        ),
> -    ])
> -
> -    for framelink, frametop in frames(L):
> -        # Dump all data slots in the (framelink, top) interval.
> -        dump.extend([
> -            dump_stack_slot(L, framelink + offset, base, top)
> -                for offset in range(frametop - framelink, 0, -1)  # noqa: E131
> -        ])
> -        # Dump frame slot (2 slots in case of GC64).
> -        dump.append(dump_framelink(L, framelink))
> -
> -    return '\n'.join(dump)
> -
> -
> -def dump_gc(g):
> -    gc = g['gc']
> -    stats = ['{key}: {value}'.format(key=f, value=gc[f]) for f in (
> -        'total', 'threshold', 'debt', 'estimate', 'stepmul', 'pause'
> -    )]
> -
> -    stats += ['sweepstr: {sweepstr}/{strmask}'.format(
> -        sweepstr=gc['sweepstr'],
> -        # String hash mask (size of hash table - 1).
> -        strmask=g['strmask'] + 1,
> -    )]
> -
> -    stats += ['{key}: {number} objects'.format(
> -        key=stat,
> -        number=handler(gc[stat])
> -    ) for stat, handler in gclen.items()]
> -
> -    return '\n'.join(map(lambda s: '\t' + s, stats))
> -
> -
> -class LJBase(gdb.Command):
> -
> -    def __init__(self, name):
> -        # XXX Fragile: though the command initialization looks like a crap but
> -        # it respects both Python 2 and Python 3.
> -        gdb.Command.__init__(self, name, gdb.COMMAND_DATA)
> -        gdb.write('{} command initialized\n'.format(name))
> -
> -
> -class LJDumpArch(LJBase):
> -    '''
> -lj-arch
> -
> -The command requires no args and dumps values of LJ_64 and LJ_GC64
> -compile-time flags. These values define the sizes of host and GC
> -pointers respectively.
> -    '''
> -
> -    def invoke(self, arg, from_tty):
> -        gdb.write(
> -            'LJ_64: {LJ_64}, LJ_GC64: {LJ_GC64}, LJ_DUALNUM: {LJ_DUALNUM}\n'
> -            .format(
> -                LJ_64=LJ_64,
> -                LJ_GC64=LJ_GC64,
> -                LJ_DUALNUM=LJ_DUALNUM
> -            )
> -        )
> -
> -
> -class LJDumpTValue(LJBase):
> -    '''
> -lj-tv <TValue *>
> -
> -The command receives a pointer to <tv> (TValue address) and dumps
> -the type and some info related to it.
> -
> -* LJ_TNIL: nil
> -* LJ_TFALSE: false
> -* LJ_TTRUE: true
> -* LJ_TLIGHTUD: light userdata @ <gcr>
> -* LJ_TSTR: string <string payload> @ <gcr>
> -* LJ_TUPVAL: upvalue @ <gcr>
> -* LJ_TTHREAD: thread @ <gcr>
> -* LJ_TPROTO: proto @ <gcr>
> -* LJ_TFUNC: <LFUNC|CFUNC|FFUNC>
> -  <LFUNC>: Lua function @ <gcr>, <nupvals> upvalues, <chunk:line>
> -  <CFUNC>: C function <mcode address>
> -  <FFUNC>: fast function #<ffid>
> -* LJ_TTRACE: trace <traceno> @ <gcr>
> -* LJ_TCDATA: cdata @ <gcr>
> -* LJ_TTAB: table @ <gcr> (asize: <asize>, hmask: <hmask>)
> -* LJ_TUDATA: userdata @ <gcr>
> -* LJ_TNUMX: number <numeric payload>
> -
> -Whether the type of the given address differs from the listed above, then
> -error message occurs.
> -    '''
> -
> -    def invoke(self, arg, from_tty):
> -        tv = cast('TValue *', parse_arg(arg))
> -        gdb.write('{}\n'.format(dump_tvalue(tv)))
> -
> -
> -class LJDumpString(LJBase):
> -    '''
> -lj-str <GCstr *>
> -
> -The command receives a <gcr> of the corresponding GCstr object and dumps
> -the payload, size in bytes and hash.
> -
> -*Caveat*: Since Python 2 provides no native Unicode support, the payload
> -is replaced with the corresponding error when decoding fails.
> -    '''
> -
> -    def invoke(self, arg, from_tty):
> -        string = cast('GCstr *', parse_arg(arg))
> -        gdb.write("String: {body} [{len} bytes] with hash {hash}\n".format(
> -            body=strdata(string),
> -            hash=strx64(string['hash']),
> -            len=string['len'],
> -        ))
> -
> -
> -class LJDumpTable(LJBase):
> -    '''
> -lj-tab <GCtab *>
> -
> -The command receives a GCtab address and dumps the table contents:
> -* Metatable address whether the one is set
> -* Array part <asize> slots:
> -  <aslot ptr>: [<index>]: <tv>
> -* Hash part <hsize> nodes:
> -  <hnode ptr>: { <tv> } => { <tv> }; next = <next hnode ptr>
> -    '''
> -
> -    def invoke(self, arg, from_tty):
> -        t = cast('GCtab *', parse_arg(arg))
> -        array = mref('TValue *', t['array'])
> -        nodes = mref('struct Node *', t['node'])
> -        mt = gcval(t['metatable'])
> -        capacity = {
> -            'apart': int(t['asize']),
> -            'hpart': int(t['hmask'] + 1) if t['hmask'] > 0 else 0
> -        }
> -
> -        if mt != 0:
> -            gdb.write('Metatable detected: {}\n'.format(strx64(mt)))
> -
> -        gdb.write('Array part: {} slots\n'.format(capacity['apart']))
> -        for i in range(capacity['apart']):
> -            slot = array + i
> -            gdb.write('{ptr}: [{index}]: {value}\n'.format(
> -                ptr=slot,
> -                index=i,
> -                value=dump_tvalue(slot)
> -            ))
> -
> -        gdb.write('Hash part: {} nodes\n'.format(capacity['hpart']))
> -        # See hmask comment in lj_obj.h
> -        for i in range(capacity['hpart']):
> -            node = nodes + i
> -            gdb.write('{ptr}: {{ {key} }} => {{ {val} }}; next = {n}\n'.format(
> -                ptr=node,
> -                key=dump_tvalue(node['key']),
> -                val=dump_tvalue(node['val']),
> -                n=mref('struct Node *', node['next'])
> -            ))
> -
> -
> -class LJDumpStack(LJBase):
> -    '''
> -lj-stack [<lua_State *>]
> -
> -The command receives a lua_State address and dumps the given Lua
> -coroutine guest stack:
> -
> -<slot ptr> [<slot attributes>] <VALUE|FRAME>
> -
> -* <slot ptr>: guest stack slot address
> -* <slot attributes>:
> -  - S: Bottom of the stack (the slot L->stack points to)
> -  - B: Base of the current guest frame (the slot L->base points to)
> -  - T: Top of the current guest frame (the slot L->top points to)
> -  - M: Last slot of the stack (the slot L->maxstack points to)
> -* <VALUE>: see help lj-tv for more info
> -* <FRAME>: framelink slot differs from the value slot: it contains info
> -  related to the function being executed within this guest frame, its
> -  type and link to the parent guest frame
> -  [<frame type>] delta=<slots in frame>, <lj-tv for LJ_TFUNC slot>
> -  - <frame type>:
> -    + L:  VM performs a call as a result of bytecode execution
> -    + C:  VM performs a call as a result of lj_vm_call
> -    + M:  VM performs a call to a metamethod as a result of bytecode
> -          execution
> -    + V:  Variable-length frame for storing arguments of a variadic
> -          function
> -    + CP: Protected C frame
> -    + PP: VM performs a call as a result of executinig pcall or xpcall
> -
> -If L is omitted the main coroutine is used.
> -    '''
> -
> -    def invoke(self, arg, from_tty):
> -        gdb.write('{}\n'.format(dump_stack(L(parse_arg(arg)))))
> -
> -
> -class LJState(LJBase):
> -    '''
> -lj-state
> -The command requires no args and dumps current VM and GC states
> -* VM state: <INTERP|C|GC|EXIT|RECORD|OPT|ASM|TRACE>
> -* GC state: <PAUSE|PROPAGATE|ATOMIC|SWEEPSTRING|SWEEP|FINALIZE|LAST>
> -* JIT state: <IDLE|ACTIVE|RECORD|START|END|ASM|ERR>
> -    '''
> -
> -    def invoke(self, arg, from_tty):
> -        g = G(L(None))
> -        gdb.write('{}\n'.format('\n'.join(
> -            map(lambda t: '{} state: {}'.format(*t), {
> -                'VM':  vm_state(g),
> -                'GC':  gc_state(g),
> -                'JIT': jit_state(g),
> -            }.items())
> -        )))
> -
> -
> -class LJGC(LJBase):
> -    '''
> -lj-gc
> -
> -The command requires no args and dumps current GC stats:
> -* total: <total number of allocated bytes in GC area>
> -* threshold: <limit when gc step is triggered>
> -* debt: <how much GC is behind schedule>
> -* estimate: <estimate of memory actually in use>
> -* stepmul: <incremental GC step granularity>
> -* pause: <pause between successive GC cycles>
> -* sweepstr: <sweep position in string table>
> -* root: <number of all collectable objects>
> -* gray: <number of gray objects>
> -* grayagain: <number of objects for atomic traversal>
> -* weak: <number of weak tables (to be cleared)>
> -* mmudata: <number of udata|cdata to be finalized>
> -    '''
> -
> -    def invoke(self, arg, from_tty):
> -        g = G(L(None))
> -        gdb.write('GC stats: {state}\n{stats}\n'.format(
> -            state=gc_state(g),
> -            stats=dump_gc(g)
> -        ))
> -
> -
> -def init(commands):
> -    global LJ_64, LJ_GC64, LJ_FR2, LJ_DUALNUM, LJ_TISNUM, PADDING
> -
> -    # XXX Fragile: though connecting the callback looks like a crap but it
> -    # respects both Python 2 and Python 3 (see #4828).
> -    def connect(callback):
> -        if LEGACY:
> -            global CONNECTED
> -            CONNECTED = True
> -        gdb.events.new_objfile.connect(callback)
> -
> -    # XXX Fragile: though disconnecting the callback looks like a crap but it
> -    # respects both Python 2 and Python 3 (see #4828).
> -    def disconnect(callback):
> -        if LEGACY:
> -            global CONNECTED
> -            if not CONNECTED:
> -                return
> -            CONNECTED = False
> -        gdb.events.new_objfile.disconnect(callback)
> -
> -    try:
> -        # Try to remove the callback at first to not append duplicates to
> -        # gdb.events.new_objfile internal list.
> -        disconnect(load)
> -    except Exception:
> -        # Callback is not connected.
> -        pass
> -
> -    try:
> -        # Detect whether libluajit objfile is loaded.
> -        gdb.parse_and_eval('luaJIT_setmode')
> -    except Exception:
> -        gdb.write('luajit-gdb.py initialization is postponed '
> -                  'until libluajit objfile is loaded\n')
> -        # Add a callback to be executed when the next objfile is loaded.
> -        connect(load)
> -        return
> -
> -    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 = gdb.lookup_global_symbol('lj_lib_checknumber') is not None
> -    except Exception:
> -        gdb.write('luajit-gdb.py failed to load: '
> -                  'no debugging symbols found for libluajit\n')
> -        return
> -
> -    for name, command in commands.items():
> -        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')
> -
> -
> -def load(event=None):
> -    init({
> -        'lj-arch':  LJDumpArch,
> -        'lj-tv':    LJDumpTValue,
> -        'lj-str':   LJDumpString,
> -        'lj-tab':   LJDumpTable,
> -        'lj-stack': LJDumpStack,
> -        'lj-state': LJState,
> -        'lj-gc':    LJGC,
> -    })
> -
> -
> -load(None)
> diff --git a/src/luajit_lldb.py b/src/luajit_dbg.py
> similarity index 63%
> rename from src/luajit_lldb.py
> rename to src/luajit_dbg.py
> index 5ac11b65..a42d8f25 100644
> --- a/src/luajit_lldb.py
> +++ b/src/luajit_dbg.py
> @@ -1,10 +1,230 @@
> -# LLDB extension for LuaJIT post-mortem analysis.
> -# To use, just put 'command script import <path-to-repo>/src/luajit_lldb.py'
> -# in lldb.
> +# Debug extension for LuaJIT post-mortem analysis.
> +# To use in LLDB: 'command script import <path-to-repo>/src/luajit_dbg.py'
> +# To use in GDB: 'source <path-to-repo>/src/luajit_dbg.py'
>   
>   import abc
>   import re
> -import lldb
> +import sys
> +import types
> +
> +from importlib import import_module
> +
> +# make script compatible with the ancient Python {{{
> +
> +
> +LEGACY = re.match(r'^2\.', sys.version)
> +
> +if LEGACY:
> +    CONNECTED = False
> +    int = long
> +    range = xrange
> +
> +
> +def is_integer_type(val):
> +    return isinstance(val, int) or (LEGACY and isinstance(val, types.IntType))
> +
> +
> +# }}}
> +
> +
> +class Debugger(object):
> +    def __init__(self):
> +        self.GDB = False
> +        self.LLDB = False
> +
> +        debuggers = {
> +            'gdb': lambda lib: True,
> +            'lldb': lambda lib: lib.debugger is not None,
> +        }
> +        for name, healthcheck in debuggers.items():
> +            lib = None
> +            try:
> +                lib = import_module(name)
> +                if healthcheck(lib):
> +                    setattr(self, name.upper(), True)
> +                    globals()[name] = lib
> +                    self.name = name
> +            except Exception:
> +                continue
> +
> +        assert self.LLDB != self.GDB
> +
> +    def setup_target(self, debugger):
> +        global target
> +        if self.LLDB:
> +            target = debugger.GetSelectedTarget()
> +
> +    def write(self, msg):
> +        if self.LLDB:
> +            print(msg)
> +        else:
> +            gdb.write(msg + '\n')
> +
> +    def cmd_init(self, cmd_cls, debugger=None):
> +        if self.LLDB:
> +            debugger.HandleCommand(
> +                'command script add --overwrite --class '
> +                'luajit_dbg.{cls} {cmd}'
> +                .format(
> +                    cls=cmd_cls.__name__,
> +                    cmd=cmd_cls.command,
> +                )
> +            )
> +        else:
> +            cmd_cls()
> +
> +    def event_connect(self, callback):
> +        if not self.LLDB:
> +            # XXX Fragile: though connecting the callback looks like a crap but
> +            # it respects both Python 2 and Python 3 (see #4828).
> +            if LEGACY:
> +                global CONNECTED
> +                CONNECTED = True
> +            gdb.events.new_objfile.connect(callback)
> +
> +    def event_disconnect(self, callback):
> +        if not self.LLDB:
> +            # XXX Fragile: though disconnecting the callback looks like a crap
> +            # but it respects both Python 2 and Python 3 (see #4828).
> +            if LEGACY:
> +                global CONNECTED
> +                if not CONNECTED:
> +                    return
> +                CONNECTED = False
> +            gdb.events.new_objfile.disconnect(callback)
> +
> +    def lookup_variable(self, name):
> +        if self.LLDB:
> +            return target.FindFirstGlobalVariable(name)
> +        else:
> +            variable, _ = gdb.lookup_symbol(name)
> +            return variable.value() if variable else None
> +
> +    def lookup_symbol(self, sym):
> +        if self.LLDB:
> +            return target.modules[0].FindSymbol(sym)
> +        else:
> +            return gdb.lookup_global_symbol(sym)
> +
> +    def to_unsigned(self, val):
> +        return val.unsigned if self.LLDB else int(val)
> +
> +    def to_signed(self, val):
> +        return val.signed if self.LLDB else int(val)
> +
> +    def to_str(self, val):
> +        return val.value if self.LLDB else str(val)
> +
> +    def find_type(self, typename):
> +        if self.LLDB:
> +            return target.FindFirstType(typename)
> +        else:
> +            return gdb.lookup_type(typename)
> +
> +    def type_to_pointer_type(self, tp):
> +        if self.LLDB:
> +            return tp.GetPointerType()
> +        else:
> +            return tp.pointer()
> +
> +    def cast_impl(self, value, t, pointer_type):
> +        if self.LLDB:
> +            if is_integer_type(value):
> +                # Integer casts require some black magic
> +                # for lldb to behave properly.
> +                if pointer_type:
> +                    return target.CreateValueFromAddress(
> +                        'value',
> +                        lldb.SBAddress(value, target),
> +                        t.GetPointeeType(),
> +                    ).address_of
> +                else:
> +                    return target.CreateValueFromData(
> +                        name='value',
> +                        data=lldb.SBData.CreateDataFromInt(value, size=8),
> +                        type=t,
> +                    )
> +            else:
> +                return value.Cast(t)
> +        else:
> +            return gdb.Value(value).cast(t)
> +
> +    def dereference(self, val):
> +        if self.LLDB:
> +            return val.Dereference()
> +        else:
> +            return val.dereference()
> +
> +    def eval(self, expression):
> +        if self.LLDB:
> +            process = target.GetProcess()
> +            thread = process.GetSelectedThread()
> +            frame = thread.GetSelectedFrame()
> +
> +            if not expression:
> +                return None
> +
> +            return frame.EvaluateExpression(expression)
> +        else:
> +            return gdb.parse_and_eval(expression)
> +
> +    def type_sizeof_impl(self, tp):
> +        if self.LLDB:
> +            return tp.GetByteSize()
> +        else:
> +            return tp.sizeof
> +
> +    def summary(self, val):
> +        if self.LLDB:
> +            return val.summary
> +        else:
> +            return str(val)[len(PADDING):].strip()
> +
> +    def type_member(self, type_obj, name):
> +        if self.LLDB:
> +            return next((x for x in type_obj.members if x.name == name), None)
> +        else:
> +            return type_obj[name]
> +
> +    def type_member_offset(self, member):
> +        if self.LLDB:
> +            return member.GetOffsetInBytes()
> +        else:
> +            return member.bitpos / 8
> +
> +    def get_member(self, value, member_name):
> +        if self.LLDB:
> +            return value.GetChildMemberWithName(member_name)
> +        else:
> +            return value[member_name]
> +
> +    def address_of(self, value):
> +        if self.LLDB:
> +            return value.address_of
> +        else:
> +            return value.address
> +
> +    def arch_init(self):
> +        global LJ_64, LJ_GC64, LJ_FR2, LJ_DUALNUM, PADDING, LJ_TISNUM, target
> +        if self.LLDB:
> +            irtype_enum = dbg.find_type('IRType').enum_members
> +            for member in irtype_enum:
> +                if member.name == 'IRT_PTR':
> +                    LJ_64 = dbg.to_unsigned(member) & 0x1f == IRT_P64
> +                if member.name == 'IRT_PGC':
> +                    LJ_GC64 = dbg.to_unsigned(member) & 0x1f == IRT_P64
> +        else:
> +            LJ_64 = str(dbg.eval('IRT_PTR')) == 'IRT_P64'
> +            LJ_GC64 = str(dbg.eval('IRT_PGC')) == 'IRT_P64'
> +
> +        LJ_FR2 = LJ_GC64
> +        LJ_DUALNUM = dbg.lookup_symbol('lj_lib_checknumber') is not None
> +        # Two extra characters are required to fit in the `0x` part.
> +        PADDING = ' ' * len(strx64(L()))
> +        LJ_TISNUM = 0xfffeffff if LJ_64 and not LJ_GC64 else LJ_T['NUMX']
> +
> +
> +dbg = Debugger()
>   
>   LJ_64 = None
>   LJ_GC64 = None
> @@ -17,68 +237,73 @@ IRT_P64 = 9
>   LJ_GCVMASK = ((1 << 47) - 1)
>   LJ_TISNUM = None
>   
> -# Debugger specific {{{
> -
> -
>   # Global
>   target = None
>   
>   
> -class Ptr:
> +class Ptr(object):
>       def __init__(self, value, normal_type):
>           self.value = value
>           self.normal_type = normal_type
>   
>       @property
>       def __deref(self):
> -        return self.normal_type(self.value.Dereference())
> +        return self.normal_type(dbg.dereference(self.value))
>   
>       def __add__(self, other):
> -        assert isinstance(other, int)
> +        assert is_integer_type(other)
>           return self.__class__(
>               cast(
>                   self.normal_type.__name__ + ' *',
>                   cast(
>                       'uintptr_t',
> -                    self.value.unsigned + other * self.value.deref.size,
> +                    dbg.to_unsigned(self.value) + other * sizeof(
> +                        self.normal_type.__name__
> +                    ),
>                   ),
>               ),
>           )
>   
>       def __sub__(self, other):
> -        assert isinstance(other, int) or isinstance(other, Ptr)
> -        if isinstance(other, int):
> +        assert is_integer_type(other) or isinstance(other, Ptr)
> +        if is_integer_type(other):
>               return self.__add__(-other)
>           else:
> -            return int((self.value.unsigned - other.value.unsigned)
> -                       / sizeof(self.normal_type.__name__))
> +            return int(
> +                (
> +                    dbg.to_unsigned(self.value) - dbg.to_unsigned(other.value)
> +                ) / sizeof(self.normal_type.__name__)
> +            )
>   
>       def __eq__(self, other):
> -        assert isinstance(other, Ptr) or isinstance(other, int) and other >= 0
> +        assert isinstance(other, Ptr) or is_integer_type(other)
>           if isinstance(other, Ptr):
> -            return self.value.unsigned == other.value.unsigned
> +            return dbg.to_unsigned(self.value) == dbg.to_unsigned(other.value)
>           else:
> -            return self.value.unsigned == other
> +            return dbg.to_unsigned(self.value) == other
>   
>       def __ne__(self, other):
>           return not self == other
>   
>       def __gt__(self, other):
>           assert isinstance(other, Ptr)
> -        return self.value.unsigned > other.value.unsigned
> +        return dbg.to_unsigned(self.value) > dbg.to_unsigned(other.value)
>   
>       def __ge__(self, other):
>           assert isinstance(other, Ptr)
> -        return self.value.unsigned >= other.value.unsigned
> +        return dbg.to_unsigned(self.value) >= dbg.to_unsigned(other.value)
>   
>       def __bool__(self):
> -        return self.value.unsigned != 0
> +        return dbg.to_unsigned(self.value) != 0
>   
>       def __int__(self):
> -        return self.value.unsigned
> +        return dbg.to_unsigned(self.value)
> +
> +    def __long__(self):
> +        return dbg.to_unsigned(self.value)
>   
>       def __str__(self):
> -        return self.value.value
> +        return dbg.to_str(self.value)
>   
>       def __getattr__(self, name):
>           if name != '__deref':
> @@ -86,53 +311,26 @@ class Ptr:
>           return self.__deref
>   
>   
> -class MetaStruct(type):
> -    def __init__(cls, name, bases, nmspc):
> -        super(MetaStruct, cls).__init__(name, bases, nmspc)
> -
> -        def make_general(field, tp):
> -            builtin = {
> -                        'uint':   'unsigned',
> -                        'int':    'signed',
> -                        'string': 'value',
> -                    }
> -            if tp in builtin.keys():
> -                return lambda self: getattr(self[field], builtin[tp])
> -            else:
> -                return lambda self: globals()[tp](self[field])
> -
> -        if hasattr(cls, 'metainfo'):
> -            for field in cls.metainfo:
> -                if not isinstance(field[0], str):
> -                    setattr(cls, field[1], field[0])
> -                else:
> -                    setattr(
> -                        cls,
> -                        field[1],
> -                        property(make_general(field[1], field[0])),
> -                    )
> -
> -
> -class Struct(metaclass=MetaStruct):
> +class Struct(object):
>       def __init__(self, value):
>           self.value = value
>   
>       def __getitem__(self, name):
> -        return self.value.GetChildMemberWithName(name)
> +        return dbg.get_member(self.value, name)
>   
>       @property
>       def addr(self):
> -        return self.value.address_of
> +        return dbg.address_of(self.value)
>   
>   
>   c_structs = {
>       'MRef': [
> -        (property(lambda self: self['ptr64'].unsigned if LJ_GC64
> -                  else self['ptr32'].unsigned), 'ptr')
> +        (property(lambda self: dbg.to_unsigned(self['ptr64']) if LJ_GC64
> +                  else dbg.to_unsigned(self['ptr32'])), 'ptr')
>       ],
>       'GCRef': [
> -        (property(lambda self: self['gcptr64'].unsigned if LJ_GC64
> -                  else self['gcptr32'].unsigned), 'gcptr')
> +        (property(lambda self: dbg.to_unsigned(self['gcptr64']) if LJ_GC64
> +                  else dbg.to_unsigned(self['gcptr32'])), 'gcptr')
>       ],
>       'TValue': [
>           ('GCRef', 'gcr'),
> @@ -141,8 +339,12 @@ c_structs = {
>           ('int', 'it64'),
>           ('string', 'n'),
>           (property(lambda self: FR(self['fr']) if not LJ_GC64 else None), 'fr'),
> -        (property(lambda self: self['ftsz'].signed if LJ_GC64 else None),
> -         'ftsz')
> +        (
> +            property(
> +                lambda self: dbg.to_signed(self['ftsz']) if LJ_GC64 else None
> +            ),
> +            'ftsz'
> +        )
>       ],
>       'GCState': [
>           ('GCRef', 'root'),
> @@ -216,26 +418,51 @@ c_structs = {
>           ('TValue', 'val'),
>           ('MRef', 'next')
>       ],
> -    'BCIns': []
> +    'BCIns': [],
>   }
>   
>   
> -for cls in c_structs.keys():
> -    globals()[cls] = type(cls, (Struct, ), {'metainfo': c_structs[cls]})
> +def make_property_from_metadata(field, tp):
> +    builtin = {
> +        'uint':   dbg.to_unsigned,
> +        'int':    dbg.to_signed,
> +        'string': dbg.to_str,
> +    }
> +    if tp in builtin.keys():
> +        return lambda self: builtin[tp](self[field])
> +    else:
> +        return lambda self: globals()[tp](self[field])
> +
> +
> +for cls, metainfo in c_structs.items():
> +    cls_dict = {}
> +    for field in metainfo:
> +        if not isinstance(field[0], str):
> +            cls_dict[field[1]] = field[0]
> +        else:
> +            cls_dict[field[1]] = property(
> +                make_property_from_metadata(field[1], field[0])
> +            )
> +    globals()[cls] = type(cls, (Struct, ), cls_dict)
>   
>   
>   for cls in Struct.__subclasses__():
>       ptr_name = cls.__name__ + 'Ptr'
>   
> +    def make_init(cls):
> +        return lambda self, value: super(type(self), self).__init__(value, cls)
> +
>       globals()[ptr_name] = type(ptr_name, (Ptr,), {
> -        '__init__':
> -            lambda self, value: super(type(self), self).__init__(value, cls)
> +        '__init__': make_init(cls)
>       })
>   
>   
> -class Command(object):
> -    def __init__(self, debugger, unused):
> -        pass
> +class Command(object if dbg.LLDB else gdb.Command):
> +    def __init__(self, debugger=None, unused=None):
> +        if dbg.GDB:
> +            # XXX Fragile: though initialization looks like a crap but it
> +            # respects both Python 2 and Python 3 (see #4828).
> +            gdb.Command.__init__(self, self.command, gdb.COMMAND_DATA)
>   
>       def get_short_help(self):
>           return self.__doc__.splitlines()[0]
> @@ -245,21 +472,15 @@ class Command(object):
>   
>       def __call__(self, debugger, command, exe_ctx, result):
>           try:
> -            self.execute(debugger, command, result)
> +            self.execute(command)
>           except Exception as e:
>               msg = 'Failed to execute command `{}`: {}'.format(self.command, e)
>               result.SetError(msg)
>   
>       def parse(self, command):
> -        process = target.GetProcess()
> -        thread = process.GetSelectedThread()
> -        frame = thread.GetSelectedFrame()
> -
>           if not command:
>               return None
> -
> -        ret = frame.EvaluateExpression(command)
> -        return ret
> +        return dbg.to_unsigned(dbg.eval(command))
>   
>       @abc.abstractproperty
>       def command(self):
> @@ -270,7 +491,7 @@ class Command(object):
>           """
>   
>       @abc.abstractmethod
> -    def execute(self, debugger, args, result):
> +    def execute(self, args):
>           """Implementation of the command.
>           Subclasses override this method to implement the logic of a given
>           command, e.g. printing a stacktrace. The command output should be
> @@ -278,6 +499,11 @@ class Command(object):
>           properly routed to LLDB frontend. Any unhandled exception will be
>           automatically transformed into proper errors.
>           """
> +    def invoke(self, arg, from_tty):
> +        try:
> +            self.execute(arg)
> +        except Exception as e:
> +            dbg.write(e)
>   
>   
>   def cast(typename, value):
> @@ -299,75 +525,38 @@ def cast(typename, value):
>               name = name[:-1].strip()
>               pointer_type = True
>   
> -    # Get the lldb type representation.
> -    t = target.FindFirstType(name)
> +    # Get the inferior type representation.
> +    t = dbg.find_type(name)
>       if pointer_type:
> -        t = t.GetPointerType()
> -
> -    if isinstance(value, int):
> -        # Integer casts require some black magic for lldb to behave properly.
> -        if pointer_type:
> -            casted = target.CreateValueFromAddress(
> -                'value',
> -                lldb.SBAddress(value, target),
> -                t.GetPointeeType(),
> -            ).address_of
> -        else:
> -            casted = target.CreateValueFromData(
> -                name='value',
> -                data=lldb.SBData.CreateDataFromInt(value, size=8),
> -                type=t,
> -            )
> -    else:
> -        casted = value.Cast(t)
> +        t = dbg.type_to_pointer_type(t)
> +
> +    casted = dbg.cast_impl(value, t, pointer_type)
>   
>       if isinstance(typename, type):
> -        # Wrap lldb object, if possible
> +        # Wrap inferior object, if possible
>           return typename(casted)
>       else:
>           return casted
>   
>   
> -def lookup_global(name):
> -    return target.FindFirstGlobalVariable(name)
> -
> -
> -def type_member(type_obj, name):
> -    return next((x for x in type_obj.members if x.name == name), None)
> -
> -
> -def find_type(typename):
> -    return target.FindFirstType(typename)
> -
> -
>   def offsetof(typename, membername):
> -    type_obj = find_type(typename)
> -    member = type_member(type_obj, membername)
> +    type_obj = dbg.find_type(typename)
> +    member = dbg.type_member(type_obj, membername)
>       assert member is not None
> -    return member.GetOffsetInBytes()
> +    return dbg.type_member_offset(member)
>   
>   
>   def sizeof(typename):
> -    type_obj = find_type(typename)
> -    return type_obj.GetByteSize()
> +    type_obj = dbg.find_type(typename)
> +    return dbg.type_sizeof_impl(type_obj)
>   
>   
>   def vtou64(value):
> -    return value.unsigned & 0xFFFFFFFFFFFFFFFF
> +    return dbg.to_unsigned(value) & 0xFFFFFFFFFFFFFFFF
>   
>   
>   def vtoi(value):
> -    return value.signed
> -
> -
> -def dbg_eval(expr):
> -    process = target.GetProcess()
> -    thread = process.GetSelectedThread()
> -    frame = thread.GetSelectedFrame()
> -    return frame.EvaluateExpression(expr)
> -
> -
> -# }}} Debugger specific
> +    return dbg.to_signed(value)
>   
>   
>   def gcval(obj):
> @@ -393,7 +582,7 @@ def gclistlen(root, end=0x0):
>   
>   
>   def gcringlen(root):
> -    if not gcref(root):
> +    if gcref(root) == 0:
>           return 0
>       elif gcref(root) == gcref(gcnext(root)):
>           return 1
> @@ -439,7 +628,7 @@ def J(g):
>       J_offset = offsetof('GG_State', 'J')
>       return cast(
>           jit_StatePtr,
> -        vtou64(cast('char *', g)) - g_offset + J_offset,
> +        int(vtou64(cast('char *', g)) - g_offset + J_offset),
>       )
>   
>   
> @@ -451,7 +640,7 @@ def L(L=None):
>       # lookup a symbol for the main coroutine considering the host app
>       # XXX Fragile: though the loop initialization looks like a crap but it
>       # respects both Python 2 and Python 3.
> -    for lstate in [L] + list(map(lambda main: lookup_global(main), (
> +    for lstate in [L] + list(map(lambda main: dbg.lookup_variable(main), (
>           # LuaJIT main coro (see luajit/src/luajit.c)
>           'globalL',
>           # Tarantool main coro (see tarantool/src/lua/init.h)
> @@ -459,7 +648,7 @@ def L(L=None):
>           # TODO: Add more
>       ))):
>           if lstate:
> -            return lua_State(lstate)
> +            return lua_StatePtr(lstate)
>   
>   
>   def tou32(val):
> @@ -523,9 +712,9 @@ def funcproto(func):
>   def strdata(obj):
>       try:
>           ptr = cast('char *', obj + 1)
> -        return ptr.summary
> +        return dbg.summary(ptr)
>       except UnicodeEncodeError:
> -        return "<luajit-lldb: error occurred while rendering non-ascii slot>"
> +        return "<luajit_dbg: error occured while rendering non-ascii slot>"
>   
>   
>   def itype(o):
> @@ -730,12 +919,12 @@ def frame_pc(framelink):
>   
>   
>   def frame_prevl(framelink):
> -    # We are evaluating the `frame_pc(framelink)[-1])` with lldb's
> +    # We are evaluating the `frame_pc(framelink)[-1])` with
>       # REPL, because the lldb API is faulty and it's not possible to cast
>       # a struct member of 32-bit type to 64-bit type without getting onto
>       # the next property bits, despite the fact that it's an actual value, not
>       # a pointer to it.
> -    bcins = vtou64(dbg_eval('((BCIns *)' + str(frame_pc(framelink)) + ')[-1]'))
> +    bcins = vtou64(dbg.eval('((BCIns *)' + str(frame_pc(framelink)) + ')[-1]'))
>       return framelink - (1 + LJ_FR2 + bc_a(bcins))
>   
>   
> @@ -789,12 +978,12 @@ def frames(L):
>   
>   def dump_framelink_slot_address(fr):
>       return '{start:{padding}}:{end:{padding}}'.format(
> -        start=hex(int(fr - 1)),
> -        end=hex(int(fr)),
> +        start=strx64(fr - 1),
> +        end=strx64(fr),
>           padding=len(PADDING),
>       ) if LJ_FR2 else '{addr:{padding}}'.format(
> -        addr=hex(int(fr)),
> -        padding=len(PADDING),
> +        addr=strx64(fr),
> +        padding=2 * len(PADDING) + 1,
>       )
>   
>   
> @@ -863,7 +1052,6 @@ def dump_stack(L, base=None, top=None):
>               nfreeslots=int((maxstack - top - 8) >> 3),
>           ),
>       ])
> -
>       for framelink, frametop in frames(L):
>           # Dump all data slots in the (framelink, top) interval.
>           dump.extend([
> @@ -904,9 +1092,11 @@ the type and some info related to it.
>   Whether the type of the given address differs from the listed above, then
>   error message occurs.
>       '''
> -    def execute(self, debugger, args, result):
> +    command = 'lj-tv'
> +
> +    def execute(self, args):
>           tvptr = TValuePtr(cast('TValue *', self.parse(args)))
> -        print('{}'.format(dump_tvalue(tvptr)))
> +        dbg.write('{}'.format(dump_tvalue(tvptr)))
>   
>   
>   class LJState(Command):
> @@ -917,9 +1107,11 @@ The command requires no args and dumps current VM and GC states
>   * GC state: <PAUSE|PROPAGATE|ATOMIC|SWEEPSTRING|SWEEP|FINALIZE|LAST>
>   * JIT state: <IDLE|ACTIVE|RECORD|START|END|ASM|ERR>
>       '''
> -    def execute(self, debugger, args, result):
> +    command = 'lj-state'
> +
> +    def execute(self, args):
>           g = G(L(None))
> -        print('{}'.format('\n'.join(
> +        dbg.write('{}'.format('\n'.join(
>               map(lambda t: '{} state: {}'.format(*t), {
>                   'VM':  vm_state(g),
>                   'GC':  gc_state(g),
> @@ -936,8 +1128,10 @@ The command requires no args and dumps values of LJ_64 and LJ_GC64
>   compile-time flags. These values define the sizes of host and GC
>   pointers respectively.
>       '''
> -    def execute(self, debugger, args, result):
> -        print(
> +    command = 'lj-arch'
> +
> +    def execute(self, args):
> +        dbg.write(
>               'LJ_64: {LJ_64}, LJ_GC64: {LJ_GC64}, LJ_DUALNUM: {LJ_DUALNUM}'
>               .format(
>                   LJ_64=LJ_64,
> @@ -965,9 +1159,11 @@ The command requires no args and dumps current GC stats:
>   * weak: <number of weak tables (to be cleared)>
>   * mmudata: <number of udata|cdata to be finalized>
>       '''
> -    def execute(self, debugger, args, result):
> +    command = 'lj-gc'
> +
> +    def execute(self, args):
>           g = G(L(None))
> -        print('GC stats: {state}\n{stats}'.format(
> +        dbg.write('GC stats: {state}\n{stats}'.format(
>               state=gc_state(g),
>               stats=dump_gc(g)
>           ))
> @@ -983,9 +1179,11 @@ the payload, size in bytes and hash.
>   *Caveat*: Since Python 2 provides no native Unicode support, the payload
>   is replaced with the corresponding error when decoding fails.
>       '''
> -    def execute(self, debugger, args, result):
> +    command = 'lj-str'
> +
> +    def execute(self, args):
>           string_ptr = GCstrPtr(cast('GCstr *', self.parse(args)))
> -        print("String: {body} [{len} bytes] with hash {hash}".format(
> +        dbg.write("String: {body} [{len} bytes] with hash {hash}".format(
>               body=strdata(string_ptr),
>               hash=strx64(string_ptr.hash),
>               len=string_ptr.len,
> @@ -1003,7 +1201,9 @@ The command receives a GCtab address and dumps the table contents:
>   * Hash part <hsize> nodes:
>     <hnode ptr>: { <tv> } => { <tv> }; next = <next hnode ptr>
>       '''
> -    def execute(self, debugger, args, result):
> +    command = 'lj-tab'
> +
> +    def execute(self, args):
>           t = GCtabPtr(cast('GCtab *', self.parse(args)))
>           array = mref(TValuePtr, t.array)
>           nodes = mref(NodePtr, t.node)
> @@ -1014,22 +1214,22 @@ The command receives a GCtab address and dumps the table contents:
>           }
>   
>           if mt:
> -            print('Metatable detected: {}'.format(strx64(mt)))
> +            dbg.write('Metatable detected: {}'.format(strx64(mt)))
>   
> -        print('Array part: {} slots'.format(capacity['apart']))
> +        dbg.write('Array part: {} slots'.format(capacity['apart']))
>           for i in range(capacity['apart']):
>               slot = array + i
> -            print('{ptr}: [{index}]: {value}'.format(
> +            dbg.write('{ptr}: [{index}]: {value}'.format(
>                   ptr=strx64(slot),
>                   index=i,
>                   value=dump_tvalue(slot)
>               ))
>   
> -        print('Hash part: {} nodes'.format(capacity['hpart']))
> +        dbg.write('Hash part: {} nodes'.format(capacity['hpart']))
>           # See hmask comment in lj_obj.h
>           for i in range(capacity['hpart']):
>               node = nodes + i
> -            print('{ptr}: {{ {key} }} => {{ {val} }}; next = {n}'.format(
> +            dbg.write('{ptr}: {{ {key} }} => {{ {val} }}; next = {n}'.format(
>                   ptr=strx64(node),
>                   key=dump_tvalue(TValuePtr(node.key.addr)),
>                   val=dump_tvalue(TValuePtr(node.val.addr)),
> @@ -1069,56 +1269,72 @@ coroutine guest stack:
>   
>   If L is omitted the main coroutine is used.
>       '''
> -    def execute(self, debugger, args, result):
> +    command = 'lj-stack'
> +
> +    def execute(self, args):
>           lstate = self.parse(args)
> -        lstate_ptr = cast('lua_State *', lstate) if coro is not None else None
> -        print('{}'.format(dump_stack(L(lstate_ptr))))
> +        lstate_ptr = cast('lua_State *', lstate) if lstate else None
> +        dbg.write('{}'.format(dump_stack(L(lstate_ptr))))
>   
>   
> -def register_commands(debugger, commands):
> -    for command, cls in commands.items():
> -        cls.command = command
> -        debugger.HandleCommand(
> -            'command script add --overwrite --class luajit_lldb.{cls} {cmd}'
> -            .format(
> -                cls=cls.__name__,
> -                cmd=cls.command,
> -            )
> -        )
> -        print('{cmd} command intialized'.format(cmd=cls.command))
> +LJ_COMMANDS = [
> +    LJDumpTValue,
> +    LJState,
> +    LJDumpArch,
> +    LJGC,
> +    LJDumpString,
> +    LJDumpTable,
> +    LJDumpStack,
> +]
> +
>   
> +def register_commands(commands, debugger=None):
> +    for cls in commands:
> +        dbg.cmd_init(cls, debugger)
> +        dbg.write('{cmd} command intialized'.format(cmd=cls.command))
>   
> -def configure(debugger):
> -    global LJ_64, LJ_GC64, LJ_FR2, LJ_DUALNUM, PADDING, LJ_TISNUM, target
> -    target = debugger.GetSelectedTarget()
> -    module = target.modules[0]
> -    LJ_DUALNUM = module.FindSymbol('lj_lib_checknumber') is not None
>   
> +def configure(debugger=None):
> +    global PADDING, LJ_TISNUM, LJ_DUALNUM
> +    dbg.setup_target(debugger)
>       try:
> -        irtype_enum = target.FindFirstType('IRType').enum_members
> -        for member in irtype_enum:
> -            if member.name == 'IRT_PTR':
> -                LJ_64 = member.unsigned & 0x1f == IRT_P64
> -            if member.name == 'IRT_PGC':
> -                LJ_FR2 = LJ_GC64 = member.unsigned & 0x1f == IRT_P64
> +        # Try to remove the callback at first to not append duplicates to
> +        # gdb.events.new_objfile internal list.
> +        dbg.event_disconnect(load)
>       except Exception:
> -        print('luajit_lldb.py failed to load: '
> -              'no debugging symbols found for libluajit')
> -        return
> -
> -    PADDING = ' ' * len(strx64((TValuePtr(L().addr))))
> -    LJ_TISNUM = 0xfffeffff if LJ_64 and not LJ_GC64 else LJ_T['NUMX']
> -
> -
> -def __lldb_init_module(debugger, internal_dict):
> -    configure(debugger)
> -    register_commands(debugger, {
> -        'lj-tv':    LJDumpTValue,
> -        'lj-state': LJState,
> -        'lj-arch':  LJDumpArch,
> -        'lj-gc':    LJGC,
> -        'lj-str':   LJDumpString,
> -        'lj-tab':   LJDumpTable,
> -        'lj-stack': LJDumpStack,
> -    })
> -    print('luajit_lldb.py is successfully loaded')
> +        # Callback is not connected.
> +        pass
> +
> +    try:
> +        # Detect whether libluajit objfile is loaded.
> +        dbg.eval('luaJIT_setmode')
> +    except Exception:
> +        dbg.write('luajit_dbg.py initialization is postponed '
> +                  'until libluajit objfile is loaded\n')
> +        # Add a callback to be executed when the next objfile is loaded.
> +        dbg.event_connect(load)
> +        return False
> +
> +    try:
> +        dbg.arch_init()
> +    except Exception:
> +        dbg.write('LuaJIT debug extension failed to load: '
> +                  'no debugging symbols found for libluajit')
> +        return False
> +    return True
> +
> +
> +# XXX: The dummy parameter is needed for this function to
> +# work as a gdb callback.
> +def load(_=None, debugger=None):
> +    if configure(debugger):
> +        register_commands(LJ_COMMANDS, debugger)
> +        dbg.write('LuaJIT debug extension is successfully loaded')
> +
> +
> +def __lldb_init_module(debugger, _=None):
> +    load(None, debugger)
> +
> +
> +if dbg.GDB:
> +    load()