cpython/Lib/dis.py at 577bd89aba39c8ba83512fcd82c421df5e41c15c · sweeneyde/cpython

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"""Disassembler of Python byte code into mnemonics."""

import sys

import types

import collections

import io

from opcode import *

from opcode import __all__ as _opcodes_all

from opcode import _nb_ops, _inline_cache_entries, _specializations, _specialized_instructions

__all__ = ["code_info", "dis", "disassemble", "distb", "disco",

"findlinestarts", "findlabels", "show_code",

"get_instructions", "Instruction", "Bytecode"] + _opcodes_all

del _opcodes_all

_have_code = (types.MethodType, types.FunctionType, types.CodeType,

classmethod, staticmethod, type)

FORMAT_VALUE = opmap['FORMAT_VALUE']

FORMAT_VALUE_CONVERTERS = (

(None, ''),

(str, 'str'),

(repr, 'repr'),

(ascii, 'ascii'),

)

MAKE_FUNCTION = opmap['MAKE_FUNCTION']

MAKE_FUNCTION_FLAGS = ('defaults', 'kwdefaults', 'annotations', 'closure')

LOAD_CONST = opmap['LOAD_CONST']

LOAD_GLOBAL = opmap['LOAD_GLOBAL']

BINARY_OP = opmap['BINARY_OP']

CACHE = opmap["CACHE"]

_all_opname = list(opname)

_all_opmap = dict(opmap)

_empty_slot = [slot for slot, name in enumerate(_all_opname) if name.startswith("<")]

for spec_op, specialized in zip(_empty_slot, _specialized_instructions):

# fill opname and opmap

_all_opname[spec_op] = specialized

_all_opmap[specialized] = spec_op

deoptmap = {

specialized: base for base, family in _specializations.items() for specialized in family

}

def _try_compile(source, name):

"""Attempts to compile the given source, first as an expression and

then as a statement if the first approach fails.

Utility function to accept strings in functions that otherwise

expect code objects

"""

try:

c = compile(source, name, 'eval')

except SyntaxError:

c = compile(source, name, 'exec')

return c

def dis(x=None, *, file=None, depth=None, show_caches=False, adaptive=False):

"""Disassemble classes, methods, functions, and other compiled objects.

With no argument, disassemble the last traceback.

Compiled objects currently include generator objects, async generator

objects, and coroutine objects, all of which store their code object

in a special attribute.

"""

if x is None:

distb(file=file, show_caches=show_caches, adaptive=adaptive)

return

# Extract functions from methods.

if hasattr(x, '__func__'):

x = x.__func__

# Extract compiled code objects from...

if hasattr(x, '__code__'): # ...a function, or

x = x.__code__

elif hasattr(x, 'gi_code'): #...a generator object, or

x = x.gi_code

elif hasattr(x, 'ag_code'): #...an asynchronous generator object, or

x = x.ag_code

elif hasattr(x, 'cr_code'): #...a coroutine.

x = x.cr_code

# Perform the disassembly.

if hasattr(x, '__dict__'): # Class or module

items = sorted(x.__dict__.items())

for name, x1 in items:

if isinstance(x1, _have_code):

print("Disassembly of %s:" % name, file=file)

try:

dis(x1, file=file, depth=depth, show_caches=show_caches, adaptive=adaptive)

except TypeError as msg:

print("Sorry:", msg, file=file)

print(file=file)

elif hasattr(x, 'co_code'): # Code object

_disassemble_recursive(x, file=file, depth=depth, show_caches=show_caches, adaptive=adaptive)

elif isinstance(x, (bytes, bytearray)): # Raw bytecode

_disassemble_bytes(x, file=file, show_caches=show_caches)

elif isinstance(x, str): # Source code

_disassemble_str(x, file=file, depth=depth, show_caches=show_caches, adaptive=adaptive)

else:

raise TypeError("don't know how to disassemble %s objects" %

type(x).__name__)

def distb(tb=None, *, file=None, show_caches=False, adaptive=False):

"""Disassemble a traceback (default: last traceback)."""

if tb is None:

try:

tb = sys.last_traceback

except AttributeError:

raise RuntimeError("no last traceback to disassemble") from None

while tb.tb_next: tb = tb.tb_next

disassemble(tb.tb_frame.f_code, tb.tb_lasti, file=file, show_caches=show_caches, adaptive=adaptive)

# The inspect module interrogates this dictionary to build its

# list of CO_* constants. It is also used by pretty_flags to

# turn the co_flags field into a human readable list.

COMPILER_FLAG_NAMES = {

1: "OPTIMIZED",

2: "NEWLOCALS",

4: "VARARGS",

8: "VARKEYWORDS",

16: "NESTED",

32: "GENERATOR",

64: "NOFREE",

128: "COROUTINE",

256: "ITERABLE_COROUTINE",

512: "ASYNC_GENERATOR",

}

def pretty_flags(flags):

"""Return pretty representation of code flags."""

names = []

for i in range(32):

flag = 1<<i

if flags & flag:

names.append(COMPILER_FLAG_NAMES.get(flag, hex(flag)))

flags ^= flag

if not flags:

break

else:

names.append(hex(flags))

return ", ".join(names)

class _Unknown:

def __repr__(self):

return "<unknown>"

# Sentinel to represent values that cannot be calculated

UNKNOWN = _Unknown()

def _get_code_object(x):

"""Helper to handle methods, compiled or raw code objects, and strings."""

# Extract functions from methods.

if hasattr(x, '__func__'):

x = x.__func__

# Extract compiled code objects from...

if hasattr(x, '__code__'): # ...a function, or

x = x.__code__

elif hasattr(x, 'gi_code'): #...a generator object, or

x = x.gi_code

elif hasattr(x, 'ag_code'): #...an asynchronous generator object, or

x = x.ag_code

elif hasattr(x, 'cr_code'): #...a coroutine.

x = x.cr_code

# Handle source code.

if isinstance(x, str):

x = _try_compile(x, "<disassembly>")

# By now, if we don't have a code object, we can't disassemble x.

if hasattr(x, 'co_code'):

return x

raise TypeError("don't know how to disassemble %s objects" %

type(x).__name__)

def _deoptop(op):

name = _all_opname[op]

return _all_opmap[deoptmap[name]] if name in deoptmap else op

def _get_code_array(co, adaptive):

return co._co_code_adaptive if adaptive else co.co_code

def code_info(x):

"""Formatted details of methods, functions, or code."""

return _format_code_info(_get_code_object(x))

def _format_code_info(co):

lines = []

lines.append("Name: %s" % co.co_name)

lines.append("Filename: %s" % co.co_filename)

lines.append("Argument count: %s" % co.co_argcount)

lines.append("Positional-only arguments: %s" % co.co_posonlyargcount)

lines.append("Kw-only arguments: %s" % co.co_kwonlyargcount)

lines.append("Number of locals: %s" % co.co_nlocals)

lines.append("Stack size: %s" % co.co_stacksize)

lines.append("Flags: %s" % pretty_flags(co.co_flags))

if co.co_consts:

lines.append("Constants:")

for i_c in enumerate(co.co_consts):

lines.append("%4d: %r" % i_c)

if co.co_names:

lines.append("Names:")

for i_n in enumerate(co.co_names):

lines.append("%4d: %s" % i_n)

if co.co_varnames:

lines.append("Variable names:")

for i_n in enumerate(co.co_varnames):

lines.append("%4d: %s" % i_n)

if co.co_freevars:

lines.append("Free variables:")

for i_n in enumerate(co.co_freevars):

lines.append("%4d: %s" % i_n)

if co.co_cellvars:

lines.append("Cell variables:")

for i_n in enumerate(co.co_cellvars):

lines.append("%4d: %s" % i_n)

return "\n".join(lines)

def show_code(co, *, file=None):

"""Print details of methods, functions, or code to *file*.

If *file* is not provided, the output is printed on stdout.

"""

print(code_info(co), file=file)

Positions = collections.namedtuple(

'Positions',

[

'lineno',

'end_lineno',

'col_offset',

'end_col_offset',

defaults=[None] * 4

)

_Instruction = collections.namedtuple(

"_Instruction",

[

'opname',

'opcode',

'arg',

'argval',

'argrepr',

'offset',

'starts_line',

'is_jump_target',

'positions'

defaults=[None]

)

_Instruction.opname.__doc__ = "Human readable name for operation"

_Instruction.opcode.__doc__ = "Numeric code for operation"

_Instruction.arg.__doc__ = "Numeric argument to operation (if any), otherwise None"

_Instruction.argval.__doc__ = "Resolved arg value (if known), otherwise same as arg"

_Instruction.argrepr.__doc__ = "Human readable description of operation argument"

_Instruction.offset.__doc__ = "Start index of operation within bytecode sequence"

_Instruction.starts_line.__doc__ = "Line started by this opcode (if any), otherwise None"

_Instruction.is_jump_target.__doc__ = "True if other code jumps to here, otherwise False"

_Instruction.positions.__doc__ = "dis.Positions object holding the span of source code covered by this instruction"

_ExceptionTableEntry = collections.namedtuple("_ExceptionTableEntry",

"start end target depth lasti")

_OPNAME_WIDTH = max(map(len, opmap))

_OPARG_WIDTH = 5

class Instruction(_Instruction):

"""Details for a bytecode operation

Defined fields:

opname - human readable name for operation

opcode - numeric code for operation

arg - numeric argument to operation (if any), otherwise None

argval - resolved arg value (if known), otherwise same as arg

argrepr - human readable description of operation argument

offset - start index of operation within bytecode sequence

starts_line - line started by this opcode (if any), otherwise None

is_jump_target - True if other code jumps to here, otherwise False

positions - Optional dis.Positions object holding the span of source code

covered by this instruction

"""

def _disassemble(self, lineno_width=3, mark_as_current=False, offset_width=4):

"""Format instruction details for inclusion in disassembly output

*lineno_width* sets the width of the line number field (0 omits it)

*mark_as_current* inserts a '-->' marker arrow as part of the line

*offset_width* sets the width of the instruction offset field

"""

fields = []

# Column: Source code line number

if lineno_width:

if self.starts_line is not None:

lineno_fmt = "%%%dd" % lineno_width

fields.append(lineno_fmt % self.starts_line)

else:

fields.append(' ' * lineno_width)

# Column: Current instruction indicator

if mark_as_current:

fields.append('-->')

else:

fields.append(' ')

# Column: Jump target marker

if self.is_jump_target:

fields.append('>>')

else:

fields.append(' ')

# Column: Instruction offset from start of code sequence

fields.append(repr(self.offset).rjust(offset_width))

# Column: Opcode name

fields.append(self.opname.ljust(_OPNAME_WIDTH))

# Column: Opcode argument

if self.arg is not None:

fields.append(repr(self.arg).rjust(_OPARG_WIDTH))

# Column: Opcode argument details

if self.argrepr:

fields.append('(' + self.argrepr + ')')

return ' '.join(fields).rstrip()

def get_instructions(x, *, first_line=None, show_caches=False, adaptive=False):

"""Iterator for the opcodes in methods, functions or code

Generates a series of Instruction named tuples giving the details of

each operations in the supplied code.

If *first_line* is not None, it indicates the line number that should

be reported for the first source line in the disassembled code.

Otherwise, the source line information (if any) is taken directly from

the disassembled code object.

"""

co = _get_code_object(x)

linestarts = dict(findlinestarts(co))

if first_line is not None:

line_offset = first_line - co.co_firstlineno

else:

line_offset = 0

return _get_instructions_bytes(_get_code_array(co, adaptive),

co._varname_from_oparg,

co.co_names, co.co_consts,

linestarts, line_offset,

co_positions=co.co_positions(),

show_caches=show_caches)

def _get_const_value(op, arg, co_consts):

"""Helper to get the value of the const in a hasconst op.

Returns the dereferenced constant if this is possible.

Otherwise (if it is a LOAD_CONST and co_consts is not

provided) returns the dis.UNKNOWN sentinel.

"""

assert op in hasconst

argval = UNKNOWN

if op == LOAD_CONST:

if co_consts is not None:

argval = co_consts[arg]

return argval

def _get_const_info(op, arg, co_consts):

"""Helper to get optional details about const references

Returns the dereferenced constant and its repr if the value

can be calculated.

Otherwise returns the sentinel value dis.UNKNOWN for the value

and an empty string for its repr.

"""

argval = _get_const_value(op, arg, co_consts)

argrepr = repr(argval) if argval is not UNKNOWN else ''

return argval, argrepr

def _get_name_info(name_index, get_name, **extrainfo):

"""Helper to get optional details about named references

Returns the dereferenced name as both value and repr if the name

list is defined.

Otherwise returns the sentinel value dis.UNKNOWN for the value

and an empty string for its repr.

"""

if get_name is not None:

argval = get_name(name_index, **extrainfo)

return argval, argval

else:

return UNKNOWN, ''

def parse_varint(iterator):

b = next(iterator)

val = b & 63

while b&64:

val <<= 6

b = next(iterator)

val |= b&63

return val

def parse_exception_table(code):

iterator = iter(code.co_exceptiontable)

entries = []

try:

while True:

start = parse_varint(iterator)*2

length = parse_varint(iterator)*2

end = start + length

target = parse_varint(iterator)*2

dl = parse_varint(iterator)

depth = dl >> 1

lasti = bool(dl&1)

entries.append(_ExceptionTableEntry(start, end, target, depth, lasti))

except StopIteration:

return entries

def _is_backward_jump(op):

name = opname[op]

return 'JUMP_BACKWARD' in name or name == "FOR_END"

def _get_instructions_bytes(code, varname_from_oparg=None,

names=None, co_consts=None,

linestarts=None, line_offset=0,

exception_entries=(), co_positions=None,

show_caches=False):

"""Iterate over the instructions in a bytecode string.

Generates a sequence of Instruction namedtuples giving the details of each

opcode. Additional information about the code's runtime environment

(e.g. variable names, co_consts) can be specified using optional

arguments.

"""

co_positions = co_positions or iter(())

get_name = None if names is None else names.__getitem__

labels = set(findlabels(code))

for start, end, target, _, _ in exception_entries:

for i in range(start, end):

labels.add(target)

starts_line = None

cache_counter = 0

for offset, op, arg in _unpack_opargs(code):

if cache_counter > 0:

if show_caches:

yield Instruction("CACHE", 0, None, None, '',

offset, None, False, None)

cache_counter -= 1

continue

if linestarts is not None:

starts_line = linestarts.get(offset, None)

if starts_line is not None:

starts_line += line_offset

is_jump_target = offset in labels

argval = None

argrepr = ''

positions = Positions(*next(co_positions, ()))

deop = _deoptop(op)

cache_counter = _inline_cache_entries[deop]

if arg is not None:

# Set argval to the dereferenced value of the argument when

# available, and argrepr to the string representation of argval.

# _disassemble_bytes needs the string repr of the

# raw name index for LOAD_GLOBAL, LOAD_CONST, etc.

argval = arg

if deop in hasconst:

argval, argrepr = _get_const_info(deop, arg, co_consts)

elif deop in hasname:

if deop == LOAD_GLOBAL:

argval, argrepr = _get_name_info(arg//2, get_name)

if (arg & 1) and argrepr:

argrepr = "NULL + " + argrepr

else:

argval, argrepr = _get_name_info(arg, get_name)

elif deop in hasjabs:

argval = arg*2

argrepr = "to " + repr(argval)

elif deop in hasjrel:

signed_arg = -arg if _is_backward_jump(deop) else arg

argval = offset + 2 + signed_arg*2

argrepr = "to " + repr(argval)

elif deop in haslocal or deop in hasfree:

argval, argrepr = _get_name_info(arg, varname_from_oparg)

elif deop in hascompare:

argval = cmp_op[arg]

argrepr = argval

elif deop == FORMAT_VALUE:

argval, argrepr = FORMAT_VALUE_CONVERTERS[arg & 0x3]

argval = (argval, bool(arg & 0x4))

if argval[1]:

if argrepr:

argrepr += ', '

argrepr += 'with format'

elif deop == MAKE_FUNCTION:

argrepr = ', '.join(s for i, s in enumerate(MAKE_FUNCTION_FLAGS)

if arg & (1<<i))

elif deop == BINARY_OP:

_, argrepr = _nb_ops[arg]

yield Instruction(_all_opname[op], op,

arg, argval, argrepr,

offset, starts_line, is_jump_target, positions)

def disassemble(co, lasti=-1, *, file=None, show_caches=False, adaptive=False):

"""Disassemble a code object."""

linestarts = dict(findlinestarts(co))

exception_entries = parse_exception_table(co)

_disassemble_bytes(_get_code_array(co, adaptive),

lasti, co._varname_from_oparg,

co.co_names, co.co_consts, linestarts, file=file,

exception_entries=exception_entries,

co_positions=co.co_positions(), show_caches=show_caches)

def _disassemble_recursive(co, *, file=None, depth=None, show_caches=False, adaptive=False):

disassemble(co, file=file, show_caches=show_caches, adaptive=adaptive)

if depth is None or depth > 0:

if depth is not None:

depth = depth - 1

for x in co.co_consts:

if hasattr(x, 'co_code'):

print(file=file)

print("Disassembly of %r:" % (x,), file=file)

_disassemble_recursive(

x, file=file, depth=depth, show_caches=show_caches, adaptive=adaptive

)

def _disassemble_bytes(code, lasti=-1, varname_from_oparg=None,

names=None, co_consts=None, linestarts=None,

*, file=None, line_offset=0, exception_entries=(),

co_positions=None, show_caches=False):

# Omit the line number column entirely if we have no line number info

show_lineno = bool(linestarts)

if show_lineno:

maxlineno = max(linestarts.values()) + line_offset

if maxlineno >= 1000:

lineno_width = len(str(maxlineno))

else:

lineno_width = 3

else:

lineno_width = 0

maxoffset = len(code) - 2

if maxoffset >= 10000:

offset_width = len(str(maxoffset))

else:

offset_width = 4

for instr in _get_instructions_bytes(code, varname_from_oparg, names,

co_consts, linestarts,

line_offset=line_offset,

exception_entries=exception_entries,

co_positions=co_positions,

show_caches=show_caches):

new_source_line = (show_lineno and

instr.starts_line is not None and

instr.offset > 0)

if new_source_line:

print(file=file)

is_current_instr = instr.offset == lasti

print(instr._disassemble(lineno_width, is_current_instr, offset_width),

file=file)

if exception_entries:

print("ExceptionTable:", file=file)

for entry in exception_entries:

lasti = " lasti" if entry.lasti else ""

end = entry.end-2

print(f" {entry.start} to {end} -> {entry.target} [{entry.depth}]{lasti}", file=file)

def _disassemble_str(source, **kwargs):

"""Compile the source string, then disassemble the code object."""

_disassemble_recursive(_try_compile(source, '<dis>'), **kwargs)

disco = disassemble # XXX For backwards compatibility

# Rely on C `int` being 32 bits for oparg

_INT_BITS = 32

# Value for c int when it overflows

_INT_OVERFLOW = 2 ** (_INT_BITS - 1)

def _unpack_opargs(code):

extended_arg = 0

for i in range(0, len(code), 2):

op = code[i]

if _deoptop(op) >= HAVE_ARGUMENT:

arg = code[i+1] | extended_arg

extended_arg = (arg << 8) if op == EXTENDED_ARG else 0

# The oparg is stored as a signed integer

# If the value exceeds its upper limit, it will overflow and wrap

# to a negative integer

if extended_arg >= _INT_OVERFLOW:

extended_arg -= 2 * _INT_OVERFLOW

else:

arg = None

extended_arg = 0

yield (i, op, arg)

def findlabels(code):

"""Detect all offsets in a byte code which are jump targets.

Return the list of offsets.

"""

labels = []

for offset, op, arg in _unpack_opargs(code):

if arg is not None:

if op in hasjrel:

if _is_backward_jump(op):

arg = -arg

label = offset + 2 + arg*2

elif op in hasjabs:

label = arg*2

else:

continue

if label not in labels:

labels.append(label)

return labels

def findlinestarts(code):

"""Find the offsets in a byte code which are start of lines in the source.

Generate pairs (offset, lineno)

"""

lastline = None

for start, end, line in code.co_lines():

if line is not None and line != lastline:

lastline = line

yield start, line

return

def _find_imports(co):

"""Find import statements in the code

Generate triplets (name, level, fromlist) where

name is the imported module and level, fromlist are

the corresponding args to __import__.

"""

IMPORT_NAME = opmap['IMPORT_NAME']

LOAD_CONST = opmap['LOAD_CONST']

consts = co.co_consts

names = co.co_names

opargs = [(op, arg) for _, op, arg in _unpack_opargs(co.co_code)

if op != EXTENDED_ARG]

for i, (op, oparg) in enumerate(opargs):

if op == IMPORT_NAME and i >= 2:

from_op = opargs[i-1]

level_op = opargs[i-2]

if (from_op[0] in hasconst and level_op[0] in hasconst):

level = _get_const_value(level_op[0], level_op[1], consts)

fromlist = _get_const_value(from_op[0], from_op[1], consts)

yield (names[oparg], level, fromlist)

def _find_store_names(co):

"""Find names of variables which are written in the code

Generate sequence of strings

"""

STORE_OPS = {

opmap['STORE_NAME'],

opmap['STORE_GLOBAL']

}

names = co.co_names

for _, op, arg in _unpack_opargs(co.co_code):

if op in STORE_OPS:

yield names[arg]

class Bytecode:

"""The bytecode operations of a piece of code

Instantiate this with a function, method, other compiled object, string of

code, or a code object (as returned by compile()).

Iterating over this yields the bytecode operations as Instruction instances.

"""

def __init__(self, x, *, first_line=None, current_offset=None, show_caches=False, adaptive=False):

self.codeobj = co = _get_code_object(x)

if first_line is None:

self.first_line = co.co_firstlineno

self._line_offset = 0

else:

self.first_line = first_line

self._line_offset = first_line - co.co_firstlineno

self._linestarts = dict(findlinestarts(co))

self._original_object = x

self.current_offset = current_offset

self.exception_entries = parse_exception_table(co)

self.show_caches = show_caches

self.adaptive = adaptive

def __iter__(self):

co = self.codeobj

return _get_instructions_bytes(_get_code_array(co, self.adaptive),

co._varname_from_oparg,

co.co_names, co.co_consts,

self._linestarts,

line_offset=self._line_offset,

exception_entries=self.exception_entries,

co_positions=co.co_positions(),

show_caches=self.show_caches)

def __repr__(self):

return "{}({!r})".format(self.__class__.__name__,

self._original_object)

@classmethod

def from_traceback(cls, tb, *, show_caches=False, adaptive=False):

""" Construct a Bytecode from the given traceback """

while tb.tb_next:

tb = tb.tb_next

return cls(

tb.tb_frame.f_code, current_offset=tb.tb_lasti, show_caches=show_caches, adaptive=adaptive

)

def info(self):

"""Return formatted information about the code object."""

return _format_code_info(self.codeobj)

def dis(self):

"""Return a formatted view of the bytecode operations."""

co = self.codeobj

if self.current_offset is not None:

offset = self.current_offset

else:

offset = -1

with io.StringIO() as output:

_disassemble_bytes(_get_code_array(co, self.adaptive),

varname_from_oparg=co._varname_from_oparg,

names=co.co_names, co_consts=co.co_consts,

linestarts=self._linestarts,

line_offset=self._line_offset,

file=output,

lasti=offset,

exception_entries=self.exception_entries,

co_positions=co.co_positions(),

show_caches=self.show_caches)

return output.getvalue()

def _test():

"""Simple test program to disassemble a file."""

import argparse

parser = argparse.ArgumentParser()

parser.add_argument('infile', type=argparse.FileType('rb'), nargs='?', default='-')

args = parser.parse_args()

with args.infile as infile:

source = infile.read()

code = compile(source, args.infile.name, "exec")

dis(code)

if __name__ == "__main__":

_test()

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