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Simplify bytecodes for try-finally, try-except and with blocks. #77568

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markshannon opened this issue Apr 29, 2018 · 14 comments
Closed

Simplify bytecodes for try-finally, try-except and with blocks. #77568

markshannon opened this issue Apr 29, 2018 · 14 comments
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3.9 only security fixes interpreter-core (Objects, Python, Grammar, and Parser dirs)

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@markshannon
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BPO 33387
Nosy @gpshead, @ncoghlan, @vstinner, @masklinn, @markshannon, @serhiy-storchaka, @csabella, @miss-islington, @iritkatriel
PRs
  • bpo-33387: Simplify bytecodes for try-finally, try-except and with blocks. #6641
  • bpo-33387: Correct release version to 3.9 for new bytecodes #17318
  • bpo-33387: Fix compiler warning in frame_block_unwind() #18099
  • bpo-33387: Correct name of bytecode in change note. #22723
  • [3.9] bpo-33387: Correct name of bytecode in change note. (GH-22723) #22765
  • bpo-33387: update documentation for exception handling opcode changes #24334
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    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 = None
closed_at = <Date 2021-01-26.10:27:14.384>
created_at = <Date 2018-04-29.18:28:42.198>
labels = ['interpreter-core', '3.9']
title = 'Simplify bytecodes for try-finally, try-except and with blocks.'
updated_at = <Date 2021-01-26.10:27:14.384>
user = 'https://github.com/markshannon'

    bugs.python.org fields:

    activity = <Date 2021-01-26.10:27:14.384>
actor = 'iritkatriel'
assignee = 'none'
closed = True
closed_date = <Date 2021-01-26.10:27:14.384>
closer = 'iritkatriel'
components = ['Interpreter Core']
creation = <Date 2018-04-29.18:28:42.198>
creator = 'Mark.Shannon'
dependencies = []
files = []
hgrepos = []
issue_num = 33387
keywords = ['patch']
message_count = 14.0
messages = ['315905', '339817', '357147', '357148', '357155', '357172', '357246', '357279', '360393', '378715', '378720', '385664', '385679', '385703']
nosy_count = 9.0
nosy_names = ['gregory.p.smith', 'ncoghlan', 'vstinner', 'xmorel', 'Mark.Shannon', 'serhiy.storchaka', 'cheryl.sabella', 'miss-islington', 'iritkatriel']
pr_nums = ['6641', '17318', '18099', '22723', '22765', '24334']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue33387'
versions = ['Python 3.9']
    @markshannon
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    The six complex bytecodes currently used for implementing 'with' and 'try' statements can be replaced with just two simpler bytecodes.
    The six bytecodes are WITH_CLEANUP_START, WITH_CLEANUP_FINISH,
    BEGIN_FINALLY, END_FINALLY, CALL_FINALLY and POP_FINALLY.
    They can be replaced with RERAISE and WITH_EXCEPT_FINISH.

    See https://bugs.python.org/issue32949 for more details of the new bytecodes and how they are used in the 'with' statement.

    The try-finally statement can be implemented broadly as
    SETUP_FINALLY except
    try-body
    POP_BLOCK
    finally-body
    JUMP exit
    except:
    finally-body
    exit:

    @markshannon markshannon added 3.8 only security fixes interpreter-core (Objects, Python, Grammar, and Parser dirs) labels Apr 29, 2018
    @csabella
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    csabella commented Apr 9, 2019

    What would be the best way to resolve the discussion between this and bpo-32949? Would it be good to try to get one of them into 3.8?

    @vstinner
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    Mark merged his PR 6641 but forgot to mention bpo-33387:

    commit fee5526
    Author: Mark Shannon <mark@hotpy.org>
    Date: Thu Nov 21 09:11:43 2019 +0000

    Produce cleaner bytecode for 'with' and 'async with' by generating separate code for normal and exceptional paths. (bpo-6641)

Remove BEGIN_FINALLY, END_FINALLY, CALL_FINALLY and POP_FINALLY bytecodes. Implement finally blocks by code duplication.
Reimplement frame.lineno setter using line numbers rather than bytecode offsets.

    @vstinner
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    The new doc seems to use Python version 3.8, but the change was merged into master which is the future Python 3.9, no?

    .. opcode:: RERAISE

     Re-raises the exception currently on top of the stack. 

 .. versionadded:: 3.8

    @markshannon
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    Thanks for noticing.
    #17318

    @markshannon
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    New changeset 82f897b by Mark Shannon in branch 'master':
    Correct release version to 3.9 for RERAISE and WITH_EXCEPT_START bytecodes. (bpo-17318)
    82f897b

    @gpshead
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    gpshead commented Nov 22, 2019

    sweet! =)

    @gpshead gpshead added 3.9 only security fixes and removed 3.8 only security fixes labels Nov 22, 2019
    @vstinner
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    Can this issue be closed now?

    @vstinner
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    New changeset 629023c by Victor Stinner in branch 'master':
    bpo-33387: Fix compiler warning in frame_block_unwind() (GH-18099)
    629023c

    @masklinn
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    masklinn mannequin commented Oct 16, 2020

    The 3.9 changelog mentions WITH_EXCEPT_FINISH but that seems to have ultimately been called WITH_EXCEPT_START, maybe it shoudl be updated also?

    @markshannon
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    Yes, thanks for pointing that out.

    @iritkatriel
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    I'm reopening this to delete an obsolete comment left behind.

    @iritkatriel iritkatriel reopened this Jan 25, 2021
    @iritkatriel iritkatriel reopened this Jan 25, 2021
    @iritkatriel
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    There's another place that needs to be updated: https://docs.python.org/3/library/dis.html#opcode-SETUP_WITH

    need to replace WITH_CLEANUP_START by WITH_EXCEPT_START

    @markshannon
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    New changeset dea5bf9 by Irit Katriel in branch 'master':
    bpo-33387: update documentation for exception handling opcode changes (GH-24334)
    dea5bf9

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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    @gpshead @vstinner @iritkatriel @markshannon @csabella