New dis.py gets tripped up by ENTER_EXECUTOR

[gvanrossum]

Bug report

Bug description:

I have some code that calls dis.dis(test, adaptive=True) where test is simple function containing a loop containing a branch. Somehow dis crashes like this:

Traceback (most recent call last):
  File "/Users/guido/cpython/t.py", line 20, in <module>
    dis.dis(test, adaptive=True)
  File "/Users/guido/cpython/Lib/dis.py", line 113, in dis
    _disassemble_recursive(x, file=file, depth=depth, show_caches=show_caches, adaptive=adaptive, show_offsets=show_offsets)
  File "/Users/guido/cpython/Lib/dis.py", line 709, in _disassemble_recursive
    disassemble(co, file=file, show_caches=show_caches, adaptive=adaptive, show_offsets=show_offsets)
  File "/Users/guido/cpython/Lib/dis.py", line 701, in disassemble
    _disassemble_bytes(_get_code_array(co, adaptive),
  File "/Users/guido/cpython/Lib/dis.py", line 754, in _disassemble_bytes
    for instr in _get_instructions_bytes(code, varname_from_oparg, names,
  File "/Users/guido/cpython/Lib/dis.py", line 668, in _get_instructions_bytes
    yield Instruction._create(op, arg, offset, start_offset, starts_line, line_number,
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/guido/cpython/Lib/dis.py", line 413, in _create
    argval, argrepr = cls._get_argval_argrepr(
                      ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/guido/cpython/Lib/dis.py", line 376, in _get_argval_argrepr
    argrepr = f"to L{labels_map[argval]}"
                     ~~~~~~~~~~^^^^^^^^
KeyError: 108

Here's the script:

def pr(i):
    pass

def is_prime(n):
    # Bogus
    return n == 2 or n == 3 or n == 5 or n == 7 or (n % 2 != 0 and n % 3 != 0 and n % 5 != 0 and n % 7 != 0)

def test():
    for i in range(2, 50):
        if is_prime(i):
            print(i)

import _testinternalcapi

_testinternalcapi.set_optimizer(_testinternalcapi.get_uop_optimizer())
test()
_testinternalcapi.set_optimizer(None)

import dis
dis.dis(test, adaptive=True)

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-112355: fix calculation of jump target of ENTER_EXECUTOR in dis #112377

[gvanrossum]

Note, to run the script, pass -Xuops or set PYTHON_UOPS=1. (Never mind, this version forces the optimizer on using _testinternalcapi.)

[iritkatriel]

I think the problem is that ENTER_EXECUTOR is interpreted as a jump (because it contains JUMPBY). So we look up the label of offset+(2*arg+1). Is it really a jump, or should it use SKIP_OVER instead of JUMPBY?

[iritkatriel]

Actually it's probably that dis assumes it's a forward jump, while it should regard it as a backward jump.