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Disassembly of Lambdas in 3.11.1 missing stack values and args #102403

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jrmccluskey opened this issue Mar 3, 2023 · 0 comments
Open

Disassembly of Lambdas in 3.11.1 missing stack values and args #102403

jrmccluskey opened this issue Mar 3, 2023 · 0 comments
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type-bug An unexpected behavior, bug, or error

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@jrmccluskey
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Bug report

I'm working on updating a type hinting and inference module in Apache Beam to support CPython 3.11 opcodes and have hit a snag working with test cases involving lambdas. The line dis.dis(lambda: {x for x in ()}, show_caches=True, adaptive=False) return the following in 3.10:

1          0 LOAD_CONST               1   (<code object <setcomp> at 0x7fd2f2b1f5d0, file "<stdin>", line 1>)
              2 LOAD_CONST               2 ('TrivialInferenceTest.testSet.<locals>.<lambda>.<locals>.<setcomp>')
              4 MAKE_FUNCTION            0
              6 LOAD_CONST               3 (())
              8 GET_ITER
             10 CALL_FUNCTION            1
             12 RETURN_VALUE

Disassembly of <code object <setcomp> at 0x7fd2f2b1f5d0, file "<stdin>", line 1>:
346           0 BUILD_SET                0
              2 LOAD_FAST                0 (.0)
        >>    4 FOR_ITER                 4 (to 14)
              6 STORE_FAST               1 (x)
              8 LOAD_FAST                1 (x)
             10 SET_ADD                  2
             12 JUMP_ABSOLUTE            2 (to 4)
        >>   14 RETURN_VALUE

But in 3.11 we get:

  1           0 RESUME                   0
              2 LOAD_CONST               1 (<code object <setcomp> at 0x7fd2f2b1f5d0, file "<stdin>", line 1>)
              4 MAKE_FUNCTION            0
              6 LOAD_CONST               2 (())
              8 GET_ITER
             10 PRECALL                  0
             12 CACHE                    0
             14 CALL                     0
             16 CACHE                    0
             18 CACHE                    0
             20 CACHE                    0
             22 CACHE                    0
             24 RETURN_VALUE

Disassembly of <code object <setcomp> at 0x7fd2f2b1f5d0, file "<stdin>", line 1>:
  1           0 RESUME                   0
              2 BUILD_SET                0
              4 LOAD_FAST                0 (.0)
        >>    6 FOR_ITER                 4 (to 16)
              8 STORE_FAST               1 (x)
             10 LOAD_FAST                1 (x)
             12 SET_ADD                  2
             14 JUMP_BACKWARD            5 (to 6)
        >>   16 RETURN_VALUE

The 3.11 output has two distinct difference: it isn't pushing a qualified name for the lambda onto the stack for MAKE_FUNCTION, and the PRECALL and CALL opcodes have args of 0 indicating that there are no args to be passed to the function despite there being a constant on the top of the stack when CALL is executed. Is this expected behavior? I haven't been able to find any documentation around lambda handling being changed, and the existing documentation for the opcodes leads me to believe this is unintended.

Your environment

  • CPython versions tested on: 3.10, 3.11
  • Operating system and architecture: Linux, x86
@jrmccluskey jrmccluskey added the type-bug An unexpected behavior, bug, or error label Mar 3, 2023
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