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Not very good strcpy implementation in cpython/Python/strdup.c #85512

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wasiher mannequin opened this issue Jul 19, 2020 · 11 comments
Closed

Not very good strcpy implementation in cpython/Python/strdup.c #85512

wasiher mannequin opened this issue Jul 19, 2020 · 11 comments
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3.10 only security fixes performance Performance or resource usage topic-C-API

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@wasiher
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wasiher mannequin commented Jul 19, 2020

BPO 41340
Nosy @benjaminp, @methane, @shihai1991, @wasiher
PRs
  • bpo-41340: Removed strcpy from strdup function #21544
  • bpo-41340: Removed fallback implementation for strdup #21634
    		•

    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 2020-07-27.03:29:02.695>
created_at = <Date 2020-07-19.10:36:04.764>
labels = ['expert-C-API', '3.10', 'performance']
title = 'Not very good strcpy implementation in cpython/Python/strdup.c'
updated_at = <Date 2020-07-27.03:29:02.694>
user = 'https://github.com/wasiher'

    bugs.python.org fields:

    activity = <Date 2020-07-27.03:29:02.694>
actor = 'methane'
assignee = 'none'
closed = True
closed_date = <Date 2020-07-27.03:29:02.695>
closer = 'methane'
components = ['C API']
creation = <Date 2020-07-19.10:36:04.764>
creator = 'fj92f3jj923f923'
dependencies = []
files = []
hgrepos = []
issue_num = 41340
keywords = ['patch']
message_count = 11.0
messages = ['373955', '373976', '373986', '373989', '374199', '374241', '374302', '374319', '374345', '374353', '374359']
nosy_count = 4.0
nosy_names = ['benjamin.peterson', 'methane', 'shihai1991', 'fj92f3jj923f923']
pr_nums = ['21544', '21634']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue41340'
versions = ['Python 3.10']
    @wasiher
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    wasiher mannequin commented Jul 19, 2020

    Hi, all!

    strdup implementation inside cpython/Python/strdup.c is not the best one.
    It calls strlen + strcpy, which is the same as calling strlen twice + memcpy.
    So I replaced it by the call of strlen + memcpy.

    It is easy to look any implementation in any library.
    Here for example:
    https://code.woboq.org/userspace/glibc/string/strdup.c.html

    So I fixed it here:
    #21544

    @wasiher wasiher mannequin added 3.10 only security fixes topic-C-API performance Performance or resource usage labels Jul 19, 2020
    @benjaminp
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    I don't think we need to spend much effort on this implementation, since it will only be used if the system libc doesn't have a strdup already.

    @wasiher
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    wasiher mannequin commented Jul 20, 2020

    Got it.
    But the fix is quite easy as I see, and does not require much affort too.

    @methane
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    methane commented Jul 20, 2020

    Can we just remove strdup.c? How about hypot.c?

    @gvanrossum
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    Either remove it or close this issue as won’t fix.

    @shihai1991
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    What's change for the performance benchmark?

    @methane
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    methane commented Jul 26, 2020

    @fj92f3jj923f923 Would you update the PR to remove the strdup.c?

    @gvanrossum
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    There’s probably also something in configure.in that can switch this on.

    @wasiher
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    wasiher mannequin commented Jul 26, 2020

    I can give a try with removing
    Please, wait
    Thanks everyone for giving a chance to make a PR :)

    @wasiher
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    wasiher mannequin commented Jul 27, 2020

    Created a new PR for removal of strdup (Hope it is correct)
    #21634
    Closed old one

    @methane
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    methane commented Jul 27, 2020

    New changeset 5798f78 by wasiher in branch 'master':
    bpo-41340: Removed fallback implementation for strdup (GH-21634)
    5798f78

    @methane methane closed this as completed Jul 27, 2020
    @methane methane closed this as completed Jul 27, 2020
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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