"""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
__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, type)
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):
"""Disassemble classes, methods, functions, or code.
With no argument, disassemble the last traceback.
"""
if x is None:
distb(file=file)
return
if hasattr(x, '__func__'): # Method
x = x.__func__
if hasattr(x, '__code__'): # Function
x = x.__code__
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)
except TypeError as msg:
print("Sorry:", msg, file=file)
print(file=file)
elif hasattr(x, 'co_code'): # Code object
disassemble(x, file=file)
elif isinstance(x, (bytes, bytearray)): # Raw bytecode
_disassemble_bytes(x, file=file)
elif isinstance(x, str): # Source code
_disassemble_str(x, file=file)
else:
raise TypeError("don't know how to disassemble %s objects" %
type(x).__name__)
def distb(tb=None, *, file=None):
"""Disassemble a traceback (default: last traceback)."""
if tb is None:
try:
tb = sys.last_traceback
except AttributeError:
raise RuntimeError("no last traceback to disassemble")
while tb.tb_next: tb = tb.tb_next
disassemble(tb.tb_frame.f_code, tb.tb_lasti, file=file)
# 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",
}
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)
def _get_code_object(x):
"""Helper to handle methods, functions, strings and raw code objects"""
if hasattr(x, '__func__'): # Method
x = x.__func__
if hasattr(x, '__code__'): # Function
x = x.__code__
if isinstance(x, str): # Source code
x = _try_compile(x, "<disassembly>")
if hasattr(x, 'co_code'): # Code object
return x
raise TypeError("don't know how to disassemble %s objects" %
type(x).__name__)
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("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)
_Instruction = collections.namedtuple("_Instruction",
"opname opcode arg argval argrepr offset starts_line is_jump_target")
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
"""
def _disassemble(self, lineno_width=3, mark_as_current=False):
"""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
"""
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(4))
# Column: Opcode name
fields.append(self.opname.ljust(20))
# Column: Opcode argument
if self.arg is not None:
fields.append(repr(self.arg).rjust(5))
# Column: Opcode argument details
if self.argrepr:
fields.append('(' + self.argrepr + ')')
return ' '.join(fields).rstrip()
def get_instructions(x, *, first_line=None):
"""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)
cell_names = co.co_cellvars + co.co_freevars
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(co.co_code, co.co_varnames, co.co_names,
co.co_consts, cell_names, linestarts,
line_offset)
def _get_const_info(const_index, const_list):
"""Helper to get optional details about const references
Returns the dereferenced constant and its repr if the constant
list is defined.
Otherwise returns the constant index and its repr().
"""
argval = const_index
if const_list is not None:
argval = const_list[const_index]
return argval, repr(argval)
def _get_name_info(name_index, name_list):
"""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 name index and its repr().
"""
argval = name_index
if name_list is not None:
argval = name_list[name_index]
argrepr = argval
else:
argrepr = repr(argval)
return argval, argrepr
def _get_instructions_bytes(code, varnames=None, names=None, constants=None,
cells=None, linestarts=None, line_offset=0):
"""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, constants) can be specified using optional
arguments.
"""
labels = findlabels(code)
extended_arg = 0
starts_line = None
free = None
# enumerate() is not an option, since we sometimes process
# multiple elements on a single pass through the loop
n = len(code)
i = 0
while i < n:
op = code[i]
offset = i
if linestarts is not None:
starts_line = linestarts.get(i, None)
if starts_line is not None:
starts_line += line_offset
is_jump_target = i in labels
i = i+1
arg = None
argval = None
argrepr = ''
if op >= HAVE_ARGUMENT:
arg = code[i] + code[i+1]*256 + extended_arg
extended_arg = 0
i = i+2
if op == EXTENDED_ARG:
extended_arg = arg*65536
# Set argval to the dereferenced value of the argument when
# availabe, 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 op in hasconst:
argval, argrepr = _get_const_info(arg, constants)
elif op in hasname:
argval, argrepr = _get_name_info(arg, names)
elif op in hasjrel:
argval = i + arg
argrepr = "to " + repr(argval)
elif op in haslocal:
argval, argrepr = _get_name_info(arg, varnames)
elif op in hascompare:
argval = cmp_op[arg]
argrepr = argval
elif op in hasfree:
argval, argrepr = _get_name_info(arg, cells)
elif op in hasnargs:
argrepr = "%d positional, %d keyword pair" % (code[i-2], code[i-1])
yield Instruction(opname[op], op,
arg, argval, argrepr,
offset, starts_line, is_jump_target)
def disassemble(co, lasti=-1, *, file=None):
"""Disassemble a code object."""
cell_names = co.co_cellvars + co.co_freevars
linestarts = dict(findlinestarts(co))
_disassemble_bytes(co.co_code, lasti, co.co_varnames, co.co_names,
co.co_consts, cell_names, linestarts, file=file)
def _disassemble_bytes(code, lasti=-1, varnames=None, names=None,
constants=None, cells=None, linestarts=None,
*, file=None, line_offset=0):
# Omit the line number column entirely if we have no line number info
show_lineno = linestarts is not None
# TODO?: Adjust width upwards if max(linestarts.values()) >= 1000?
lineno_width = 3 if show_lineno else 0
for instr in _get_instructions_bytes(code, varnames, names,
constants, cells, linestarts,
line_offset=line_offset):
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), file=file)
def _disassemble_str(source, *, file=None):
"""Compile the source string, then disassemble the code object."""
disassemble(_try_compile(source, '<dis>'), file=file)
disco = disassemble # XXX For backwards compatibility
def findlabels(code):
"""Detect all offsets in a byte code which are jump targets.
Return the list of offsets.
"""
labels = []
# enumerate() is not an option, since we sometimes process
# multiple elements on a single pass through the loop
n = len(code)
i = 0
while i < n:
op = code[i]
i = i+1
if op >= HAVE_ARGUMENT:
arg = code[i] + code[i+1]*256
i = i+2
label = -1
if op in hasjrel:
label = i+arg
elif op in hasjabs:
label = arg
if label >= 0:
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) as described in Python/compile.c.
"""
byte_increments = list(code.co_lnotab[0::2])
line_increments = list(code.co_lnotab[1::2])
lastlineno = None
lineno = code.co_firstlineno
addr = 0
for byte_incr, line_incr in zip(byte_increments, line_increments):
if byte_incr:
if lineno != lastlineno:
yield (addr, lineno)
lastlineno = lineno
addr += byte_incr
lineno += line_incr
if lineno != lastlineno:
yield (addr, lineno)
class Bytecode:
"""The bytecode operations of a piece of code
Instantiate this with a function, method, 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):
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._cell_names = co.co_cellvars + co.co_freevars
self._linestarts = dict(findlinestarts(co))
self._original_object = x
self.current_offset = current_offset
def __iter__(self):
co = self.codeobj
return _get_instructions_bytes(co.co_code, co.co_varnames, co.co_names,
co.co_consts, self._cell_names,
self._linestarts,
line_offset=self._line_offset)
def __repr__(self):
return "{}({!r})".format(self.__class__.__name__,
self._original_object)
@classmethod
def from_traceback(cls, tb):
""" 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)
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(co.co_code, varnames=co.co_varnames,
names=co.co_names, constants=co.co_consts,
cells=self._cell_names,
linestarts=self._linestarts,
line_offset=self._line_offset,
file=output,
lasti=offset)
return output.getvalue()
def _test():
"""Simple test program to disassemble a file."""
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('infile', type=argparse.FileType(), 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()
