`sys.settrace` does not receive `opcode` events in 3.12.x

[rijenkii]

Bug report

Bug description:

import sys
from types import FrameType
from typing import Any


def trace(frame: FrameType, event: str, arg: Any):
    frame.f_trace_opcodes = True
    print(frame, event, arg)
    return trace


sys.settrace(trace)

eval('"-".join([x for x in "hello"])')

When running in versions 3.11.7 and 3.13.0a3, opcode events are emitted, though they differ:

podman run --rm -it -v (pwd)/tracetest.py:/tracetest.py:Z python:3.11.7 python /tracetest.py

<frame at 0x7fd3ac579bc0, file '<string>', line 0, code <module>> call None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> line None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> call None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> line None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> line None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> line None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> line None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> line None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> line None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> opcode None
<frame at 0x7fd3ac57a400, file '<string>', line 1, code <listcomp>> return ['h', 'e', 'l', 'l', 'o']
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> opcode None
<frame at 0x7fd3ac579bc0, file '<string>', line 1, code <module>> return h-e-l-l-o

podman run --rm -it -v (pwd)/tracetest.py:/tracetest.py:Z python:3.13.0a3 python /tracetest.py

<frame at 0x7f79bcabca00, file '<string>', line 0, code <module>> call None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> line None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> line None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> line None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> line None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> line None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> line None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> opcode None
<frame at 0x7f79bcabca00, file '<string>', line 1, code <module>> return h-e-l-l-o

However on 3.12.0 and 3.12.1, only call, line and return are emitted:

podman run --rm -it -v (pwd)/tracetest.py:/tracetest.py:Z python:3.12.1 python /tracetest.py

<frame at 0x7ff4180afc40, file '<string>', line 0, code <module>> call None
<frame at 0x7ff4180afc40, file '<string>', line 1, code <module>> line None
<frame at 0x7ff4180afc40, file '<string>', line 1, code <module>> line None
<frame at 0x7ff4180afc40, file '<string>', line 1, code <module>> line None
<frame at 0x7ff4180afc40, file '<string>', line 1, code <module>> line None
<frame at 0x7ff4180afc40, file '<string>', line 1, code <module>> line None
<frame at 0x7ff4180afc40, file '<string>', line 1, code <module>> line None
<frame at 0x7ff4180afc40, file '<string>', line 1, code <module>> return h-e-l-l-o

CPython versions tested on:

3.12

Operating systems tested on:

Linux

Linked PRs

• [3.12] gh-114480: Add docs for f_trace_opcodes behavior on 3.12 #114540

[terryjreedy]

Verified on Windows.

[gaogaotiantian]

dup #103615 which is fixed in main by #109472

This is an issue introduced by PEP 669 and it's a design issue. The workaround is to set any f_trace_opcodes before sys.settrace. I doubt if we can backport the fix to 3.12 because it's a relatively large design level change. I would guess we will "leave 3.12 as it is".

[rijenkii]

If fix is not backportable then I would prefer this bug and the workaround to be documented somewhere, preferrably in the settrace documentation.

[gaogaotiantian]

I'm not against documenting this for 3.12 only. We need to consult docs team about how to do this properly.

[jasfvcb]

太对了

[gaogaotiantian]

This behavior is documented in 3.12, so close this issue.