dis(): This had a problem with proto 0 pickles, in that POP sometimes
popped a MARK, but without stack emulation the disassembler couldn't know that, and subsequent indentation got hosed. Now the disassembler does do enough stack emulation to catch this. While I was at it, also added lots of sanity checks for other stack operations, and correct use of the memo. This goes (I think) a long way toward being a "pickle verifier" now too.
This commit is contained in:
Tim Peters
parent
5d9113d8be
commit
c1c2b3e0e2
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@ -13,10 +13,11 @@ dis(pickle, out=None, indentlevel=4)
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# Other ideas:
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#
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# - A pickle verifier: read a pickle and check it exhaustively for
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# well-formedness.
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# well-formedness. dis() does a lot of this already.
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#
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# - A protocol identifier: examine a pickle and return its protocol number
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# (== the highest .proto attr value among all the opcodes in the pickle).
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# dis() already prints this info at the end.
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#
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# - A pickle optimizer: for example, tuple-building code is sometimes more
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# elaborate than necessary, catering for the possibility that the tuple
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@ -712,6 +713,9 @@ class StackObject(object):
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assert isinstance(doc, str)
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self.doc = doc
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def __repr__(self):
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return self.name
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pyint = StackObject(
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name='int',
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@ -1858,10 +1862,33 @@ def dis(pickle, out=None, indentlevel=4):
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Optional arg indentlevel is the number of blanks by which to indent
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a new MARK level. It defaults to 4.
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In addition to printing the disassembly, some sanity checks are made:
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+ All embedded opcode arguments "make sense".
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+ Explicit and implicit pop operations have enough items on the stack.
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+ When an opcode implicitly refers to a markobject, a markobject is
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actually on the stack.
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+ A memo entry isn't referenced before it's defined.
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+ The markobject isn't stored in the memo.
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+ A memo entry isn't redefined.
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"""
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markstack = []
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# Most of the hair here is for sanity checks, but most of it is needed
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# anyway to detect when a protocol 0 POP takes a MARK off the stack
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# (which in turn is needed to indent MARK blocks correctly).
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stack = [] # crude emulation of unpickler stack
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memo = {} # crude emulation of unpicker memo
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maxproto = -1 # max protocol number seen
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markstack = [] # bytecode positions of MARK opcodes
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indentchunk = ' ' * indentlevel
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errormsg = None
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for opcode, arg, pos in genops(pickle):
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if pos is not None:
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print >> out, "%5d:" % pos,
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@ -1870,12 +1897,54 @@ def dis(pickle, out=None, indentlevel=4):
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indentchunk * len(markstack),
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opcode.name)
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maxproto = max(maxproto, opcode.proto)
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# See whether a MARK should be popped.
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before = opcode.stack_before # don't mutate
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after = opcode.stack_after # don't mutate
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markmsg = None
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if markstack and markobject in opcode.stack_before:
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assert markobject not in opcode.stack_after
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markpos = markstack.pop()
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if markpos is not None:
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markmsg = "(MARK at %d)" % markpos
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if markobject in before or (opcode.name == "POP" and
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stack and
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stack[-1] is markobject):
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assert markobject not in after
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if markstack:
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markpos = markstack.pop()
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if markpos is None:
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markmsg = "(MARK at unknown opcode offset)"
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else:
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markmsg = "(MARK at %d)" % markpos
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# Pop everything at and after the topmost markobject.
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while stack[-1] is not markobject:
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stack.pop()
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stack.pop()
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# Remove markobject stuff from stack_before.
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try:
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i = before.index(markobject)
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before = before[:i]
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except ValueError:
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assert opcode.name == "POP"
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assert len(before) == 1
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before = [] # stop code later from popping again
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else:
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errormsg = markmsg = "no MARK exists on stack"
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# Check for correct memo usage.
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if opcode.name in ("PUT", "BINPUT", "LONG_BINPUT"):
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if arg in memo:
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errormsg = "memo key %r already defined" % arg
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elif not stack:
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errormsg = "stack is empty -- can't store into memo"
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elif stack[-1] is markobject:
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errormsg = "can't store markobject in the memo"
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else:
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memo[arg] = stack[-1]
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elif opcode.name in ("GET", "BINGET", "LONG_BINGET"):
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if arg in memo:
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assert len(after) == 1
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after = [memo[arg]] # for better stack emulation
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else:
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errormsg = "memo key %r has never been stored into" % arg
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if arg is not None or markmsg:
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# make a mild effort to align arguments
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@ -1886,10 +1955,27 @@ def dis(pickle, out=None, indentlevel=4):
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line += ' ' + markmsg
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print >> out, line
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if markobject in opcode.stack_after:
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if errormsg:
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# Note that we delayed complaining until the offending opcode
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# was printed.
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raise ValueError(errormsg)
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# Emulate the stack effects.
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n = len(before)
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if len(stack) < n:
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raise ValueError("tried to pop %d items from stack with "
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"only %d items" % (n, len(stack)))
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if n:
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del stack[-n:]
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if markobject in after:
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assert markobject not in opcode.stack_before
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markstack.append(pos)
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stack.extend(after)
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print >> out, "highest protocol among opcodes =", maxproto
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if stack:
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raise ValueError("stack not empty after STOP: %r" % stack)
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_dis_test = r"""
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>>> import pickle
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@ -1919,6 +2005,7 @@ _dis_test = r"""
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48: s SETITEM
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49: a APPEND
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50: . STOP
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highest protocol among opcodes = 0
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Try again with a "binary" pickle.
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@ -1943,6 +2030,7 @@ Try again with a "binary" pickle.
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36: s SETITEM
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37: e APPENDS (MARK at 3)
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38: . STOP
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highest protocol among opcodes = 1
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Exercise the INST/OBJ/BUILD family.
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@ -1951,6 +2039,7 @@ Exercise the INST/OBJ/BUILD family.
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0: c GLOBAL 'random random'
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15: p PUT 0
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18: . STOP
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highest protocol among opcodes = 0
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>>> x = [pickle.PicklingError()] * 2
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>>> dis(pickle.dumps(x, 0))
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@ -1973,6 +2062,7 @@ Exercise the INST/OBJ/BUILD family.
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52: g GET 1
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55: a APPEND
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56: . STOP
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highest protocol among opcodes = 0
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>>> dis(pickle.dumps(x, 1))
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0: ] EMPTY_LIST
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@ -1993,6 +2083,7 @@ Exercise the INST/OBJ/BUILD family.
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46: h BINGET 2
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48: e APPENDS (MARK at 3)
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49: . STOP
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highest protocol among opcodes = 1
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Try "the canonical" recursive-object test.
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@ -2017,6 +2108,8 @@ True
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10: p PUT 1
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13: a APPEND
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14: . STOP
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highest protocol among opcodes = 0
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>>> dis(pickle.dumps(L, 1))
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0: ] EMPTY_LIST
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1: q BINPUT 0
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@ -2026,13 +2119,11 @@ True
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7: q BINPUT 1
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9: a APPEND
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10: . STOP
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highest protocol among opcodes = 1
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The protocol 0 pickle of the tuple causes the disassembly to get confused,
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as it doesn't realize that the POP opcode at 16 gets rid of the MARK at 0
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(so the output remains indented until the end). The protocol 1 pickle
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doesn't trigger this glitch, because the disassembler realizes that
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POP_MARK gets rid of the MARK. Doing a better job on the protocol 0
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pickle would require the disassembler to emulate the stack.
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Note that, in the protocol 0 pickle of the recursive tuple, the disassembler
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has to emulate the stack in order to realize that the POP opcode at 16 gets
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rid of the MARK at 0.
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>>> dis(pickle.dumps(T, 0))
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0: ( MARK
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@ -2045,9 +2136,11 @@ pickle would require the disassembler to emulate the stack.
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11: p PUT 1
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14: a APPEND
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15: 0 POP
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16: 0 POP
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17: g GET 1
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20: . STOP
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16: 0 POP (MARK at 0)
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17: g GET 1
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20: . STOP
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highest protocol among opcodes = 0
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>>> dis(pickle.dumps(T, 1))
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0: ( MARK
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1: ] EMPTY_LIST
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@ -2060,6 +2153,7 @@ pickle would require the disassembler to emulate the stack.
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11: 1 POP_MARK (MARK at 0)
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12: h BINGET 1
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14: . STOP
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highest protocol among opcodes = 1
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Try protocol 2.
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@ -2072,6 +2166,7 @@ Try protocol 2.
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8: q BINPUT 1
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10: a APPEND
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11: . STOP
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highest protocol among opcodes = 2
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>>> dis(pickle.dumps(T, 2))
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0: \x80 PROTO 2
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@ -2084,6 +2179,7 @@ Try protocol 2.
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11: 0 POP
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12: h BINGET 1
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14: . STOP
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highest protocol among opcodes = 2
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"""
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__test__ = {'disassembler_test': _dis_test,
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