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f_trace_opcodes frame attribute to switch to per-opcode tracing #75525

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ncoghlan opened this issue Sep 4, 2017 · 6 comments
Closed

f_trace_opcodes frame attribute to switch to per-opcode tracing #75525

ncoghlan opened this issue Sep 4, 2017 · 6 comments
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3.7 type-feature

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@ncoghlan
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@ncoghlan ncoghlan commented Sep 4, 2017

BPO 31344
Nosy @gpshead, @ncoghlan, @nedbat, @njsmith, @serhiy-storchaka, @zooba
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  • #3417
  • Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = 'https://github.com/ncoghlan'
    closed_at = <Date 2017-09-08.00:14:59.760>
    created_at = <Date 2017-09-04.22:03:40.531>
    labels = ['type-feature', '3.7']
    title = 'f_trace_opcodes frame attribute to switch to per-opcode tracing'
    updated_at = <Date 2017-09-08.00:14:59.759>
    user = 'https://github.com/ncoghlan'

    bugs.python.org fields:

    activity = <Date 2017-09-08.00:14:59.759>
    actor = 'ncoghlan'
    assignee = 'ncoghlan'
    closed = True
    closed_date = <Date 2017-09-08.00:14:59.760>
    closer = 'ncoghlan'
    components = []
    creation = <Date 2017-09-04.22:03:40.531>
    creator = 'ncoghlan'
    dependencies = []
    files = []
    hgrepos = []
    issue_num = 31344
    keywords = []
    message_count = 6.0
    messages = ['301273', '301362', '301366', '301374', '301565', '301655']
    nosy_count = 6.0
    nosy_names = ['gregory.p.smith', 'ncoghlan', 'nedbat', 'njs', 'serhiy.storchaka', 'steve.dower']
    pr_nums = ['3417']
    priority = 'normal'
    resolution = 'fixed'
    stage = 'resolved'
    status = 'closed'
    superseder = None
    type = 'enhancement'
    url = 'https://bugs.python.org/issue31344'
    versions = ['Python 3.7']

    @ncoghlan
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    @ncoghlan ncoghlan commented Sep 4, 2017

    In order to test bpo-29988 reliably, we want the ability to run trace hooks for every opcode in a frame, rather than for every line.

    The simplest API we've been able to come up with for that is a "f_trace_opcodes" attribute on the frame which we set from the trace hook the first time that it runs.

    @ncoghlan ncoghlan added 3.7 type-feature labels Sep 4, 2017
    @serhiy-storchaka
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    @serhiy-storchaka serhiy-storchaka commented Sep 5, 2017

    The f_trace attribute is writable from a tracing function. There are different restrictions, for example you can't jump inside a 'for' loop from outside. The code of the setter is complex and hard for modifications (see the discussion on PR 2827). Allowing to trace opcodes can make it more complex.

    @njsmith
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    @njsmith njsmith commented Sep 5, 2017

    Adding Ned to CC in case he wants to comment on the utility of per-opcode tracing from the perspective of coverage.py.

    @ncoghlan
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    @ncoghlan ncoghlan commented Sep 5, 2017

    Steve's also requested the ability to *turn off* line debugging, and I'm thinking it may make sense to allow all four configurations:

    • both line and opcode events disabled
    • only getting one or the other
    • getting both kinds of event

    Opcode events would definitely be off by default, and if you do turn them on, then you'd be in a situation similar to importing ctypes: the interpreter is no longer guaranteed to work correctly. (Although unlike ctypes, you shouldn't get segfaults because of it)

    @ncoghlan ncoghlan self-assigned this Sep 7, 2017
    @ncoghlan
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    @ncoghlan ncoghlan commented Sep 7, 2017

    My posted PR implements the "independent flags" option, where f_trace_lines and f_trace_opcodes allow per-line and per-opcode events to be requested independently.

    The default is to emit per-line events (as has historically been the case).

    @ncoghlan
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    @ncoghlan ncoghlan commented Sep 8, 2017

    New changeset 5a85167 by Nick Coghlan in branch 'master':
    bpo-31344: Per-frame control of trace events (GH-3417)
    5a85167

    @ncoghlan ncoghlan closed this Sep 8, 2017
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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