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dis.py
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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 __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'] 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, generators, 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, 'gi_code'): # Generator x = x.gi_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", 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) def _get_code_object(x): """Helper to handle methods, functions, generators, strings and raw code objects""" if hasattr(x, '__func__'): # Method x = x.__func__ if hasattr(x, '__code__'): # Function x = x.__code__ if hasattr(x, 'gi_code'): # Generator x = x.gi_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") _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" 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) starts_line = None for offset, op, arg in _unpack_opargs(code): 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 = '' 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 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 = offset + 2 + 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 == FORMAT_VALUE: argval = ((None, str, repr, ascii)[arg & 0x3], bool(arg & 0x4)) argrepr = ('', 'str', 'repr', 'ascii')[arg & 0x3] if argval[1]: if argrepr: argrepr += ', ' argrepr += 'with format' 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 _unpack_opargs(code): extended_arg = 0 for i in range(0, len(code), 2): op = code[i] if op >= HAVE_ARGUMENT: arg = code[i+1] | extended_arg extended_arg = (arg << 8) if op == EXTENDED_ARG else 0 else: arg = None 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: label = offset + 2 + arg elif op in hasjabs: label = arg 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) as described in Python/compile.c. """ byte_increments = code.co_lnotab[0::2] line_increments = 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 if line_incr >= 0x80: # line_increments is an array of 8-bit signed integers line_incr -= 0x100 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()