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bpo-46724: Use JUMP_ABSOLUTE for all backward jumps. (GH-31326)

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* Make sure all backward jumps use JUMP_ABSOLUTE.

* Add news.

* Fix up news item.

* Make test use consistent style.
This commit is contained in:
Mark Shannon 2022-02-15 09:35:16 +00:00 committed by GitHub
parent 12360aa159
commit 3be1a443ca
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3 changed files with 17 additions and 0 deletions
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10
Lib/test/test_compile.py
View file

@ -1008,6 +1008,16 @@ def if_else_break():
elif instr.opname in HANDLED_JUMPS:
self.assertNotEqual(instr.arg, (line + 1)*INSTR_SIZE)
def test_no_wraparound_jump(self):
# See https://bugs.python.org/issue46724
def while_not_chained(a, b, c):
while not (a < b < c):
pass
for instr in dis.Bytecode(while_not_chained):
self.assertNotEqual(instr.opname, "EXTENDED_ARG")
@requires_debug_ranges()
class TestSourcePositions(unittest.TestCase):
# Ensure that compiled code snippets have correct line and column numbers

2
Misc/NEWS.d/next/Core and Builtins/2022-02-14-14-44-06.bpo-46724.jym_K6.rst Normal file
View file

@ -0,0 +1,2 @@
Make sure that all backwards jumps use the ``JUMP_ABSOLUTE`` instruction, rather
than ``JUMP_FORWARD`` with an argument of ``(2**32)+offset``.

5
Python/compile.c
View file

@ -7534,6 +7534,11 @@ normalize_jumps(struct assembler *a)
last->i_opcode = JUMP_FORWARD;
}
}
if (last->i_opcode == JUMP_FORWARD) {
if (last->i_target->b_visited == 1) {
last->i_opcode = JUMP_ABSOLUTE;
}
}
}
}