8000 bpo-46724: Fix dis support for overflow args (GH-31285) · python/cpython@c3ce778 · GitHub
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saulshanabrooksaulshanabrook
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bpo-46724: Fix dis support for overflow args (GH-31285)
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3 files changed

+40
-5
lines changed

3 files changed

+40
-5
lines changed

‎Lib/dis.py

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Original file line numberDiff line numberDiff line change
@@ -515,13 +515,24 @@ def _disassemble_str(source, **kwargs):
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disco = disassemble # XXX For backwards compatibility
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# Rely on C `int` being 32 bits for oparg
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_INT_BITS = 32
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# Value for c int when it overflows
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_INT_OVERFLOW = 2 ** (_INT_BITS - 1)
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def _unpack_opargs(code):
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extended_arg = 0
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for i in range(0, len(code), 2):
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op = code[i]
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if op >= HAVE_ARGUMENT:
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arg = code[i+1] | extended_arg
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extended_arg = (arg << 8) if op == EXTENDED_ARG else 0
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# The oparg is stored as a signed integer
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# If the value exceeds its upper limit, it will overflow and wrap
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# to a negative integer
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if extended_arg >= _INT_OVERFLOW:
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extended_arg -= 2 * _INT_OVERFLOW
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else:
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arg = None
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extended_arg = 0

‎Lib/test/test_dis.py

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Original file line numberDiff line numberDiff line change
@@ -1,14 +1,17 @@
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# Minimal tests for dis module
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from test.support import captured_stdout, requires_debug_ranges
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from test.support.bytecode_helper import BytecodeTestCase
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import unittest
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import sys
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import contextlib
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import dis
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import io
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import re
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import sys
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import types
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import contextlib
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import unittest
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from test.support import captured_stdout, requires_debug_ranges
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from test.support.bytecode_helper import BytecodeTestCase
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import opcode
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def get_tb():
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def _error():
@@ -219,6 +222,22 @@ def bug42562():
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RETURN_VALUE
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"""
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# [255, 255, 255, 252] is -4 in a 4 byte signed integer
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bug46724 = bytes([
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opcode.EXTENDED_ARG, 255,
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opcode.EXTENDED_ARG, 255,
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opcode.EXTENDED_ARG, 255,
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opcode.opmap['JUMP_FORWARD'], 252,
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])
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dis_bug46724 = """\
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>> EXTENDED_ARG 255
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EXTENDED_ARG 65535
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EXTENDED_ARG 16777215
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JUMP_FORWARD -4 (to 0)
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"""
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_BIG_LINENO_FORMAT = """\
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1 RESUME 0
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@@ -688,6 +707,10 @@ def test_bug_45757(self):
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# Extended arg followed by NOP
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self.do_disassembly_test(code_bug_45757, dis_bug_45757)
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def test_bug_46724(self):
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# Test that negative operargs are handled properly
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self.do_disassembly_test(bug46724, dis_bug46724)
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def test_big_linenos(self):
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def func(count):
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namespace = {}

‎Misc/NEWS.d/next/Library/2022-02-11-20-41-17.bpo-46724.eU52_N.rst

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
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Fix :mod:`dis` behavior on negative jump offsets.

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