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find_library broken for binutils >= 2.32 / 2.34 #84916

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Closed as not planned
find_library broken for binutils >= 2.32 / 2.34#84916
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3.10 (EOL)end of life3.7 (EOL)end of life3.8 (EOL)end of life3.9 (EOL)end of lifetopic-ctypestype-bugAn unexpected behavior, bug, or error

Description

@FRidh
FRidh
mannequin
opened on May 23, 2020
BPO 40739
Nosy @vsajip, @amauryfa, @abalkin, @meadori, @FRidh

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 = None
created_at = <Date 2020-05-23.07:41:27.686>
labels = ['type-bug', '3.8', '3.9', '3.10', 'ctypes', '3.7']
title = 'find_library broken for binutils >= 2.32 / 2.34'
updated_at = <Date 2020-05-24.08:50:11.618>
user = 'https://github.com/FRidh'

bugs.python.org fields:

activity = <Date 2020-05-24.08:50:11.618>
actor = 'SilentGhost'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['ctypes']
creation = <Date 2020-05-23.07:41:27.686>
creator = 'Frederik Rietdijk'
dependencies = []
files = []
hgrepos = []
issue_num = 40739
keywords = []
message_count = 2.0
messages = ['369699', '369701']
nosy_count = 5.0
nosy_names = ['vinay.sajip', 'amaury.forgeotdarc', 'belopolsky', 'meador.inge', 'Frederik Rietdijk']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue40739'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9', 'Python 3.10']

Activity

  1. FRidh commented on May 23, 2020

    @FRidh
    FRidhmannequin
    on May 23, 2020
    MannequinAuthor

    With binutils 2.34 Python 3 (any version) the following returns None

    python3 -c 'import ctypes.util; print((ctypes.util.find_library("c")))'

    instead of the requested library which we think may be caused by https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=727a29badd95a68d08b86fec0b98702ce756c660
    which is included in binutils 2.32 and up.

    With binutils at 2.31 we got

    # recent unstable
    $ nix-shell --pure -p hello --run 'ld -t -o /dev/null -lc'
    /nix/store/a57856fs4m8ir6vlv14h3gq3sv9aq2lb-binutils-2.31.1/bin/ld: mode elf_x86_64
    /nix/store/nwsn18fysga1n5s0bj4jp4wfwvlbx8b1-glibc-2.30/lib/libc.so.6
    /nix/store/nwsn18fysga1n5s0bj4jp4wfwvlbx8b1-glibc-2.30/lib/ld-linux-x86-64.so.2
    /nix/store/nwsn18fysga1n5s0bj4jp4wfwvlbx8b1-glibc-2.30/lib/ld-linux-x86-64.so.2
    /nix/store/a57856fs4m8ir6vlv14h3gq3sv9aq2lb-binutils-2.31.1/bin/ld: warning: cannot find entry symbol _start; not setting start address

    however with 2.34 we get

    # current staging
    $ nix-shell --pure -p hello --run 'ld -t -o /dev/null -lc'
    /nix/store/j1l6ds4mhm97nqw965w9sg07i9fric4d-glibc-2.30/lib/libc.so
    /nix/store/j1l6ds4mhm97nqw965w9sg07i9fric4d-glibc-2.30/lib/libc.so.6
    /nix/store/j1l6ds4mhm97nqw965w9sg07i9fric4d-glibc-2.30/lib/libc_nonshared.a
    /nix/store/j1l6ds4mhm97nqw965w9sg07i9fric4d-glibc-2.30/lib/ld-linux-x86-64.so.2
    /nix/store/j1l6ds4mhm97nqw965w9sg07i9fric4d-glibc-2.30/lib/libc_nonshared.a
    /nix/store/j1l6ds4mhm97nqw965w9sg07i9fric4d-glibc-2.30/lib/ld-linux-x86-64.so.2
    /nix/store/j284mk8hdv9ccxfdlhcdk1lg2jml4fhk-binutils-2.34/bin/ld: warning: cannot find entry symbol _start; not setting start address

    The text-file libc.so is present which find_library cannot handle.

    I suppose the regex needs to be fixed to exclude these references or otherwise handle them. It may be a bit late for binutils to revert their change.

    Note this issue was discovered with the CFFI test suite https://foss.heptapod.net/pypy/cffi/blob/2aa5775ffdd6a911e9f40e3c2f5ba766155349c5/c/test_c.py#L60

    Nixpkgs issue: NixOS/nixpkgs#86954 (comment)

  2. FRidh
    added
    3.10 (EOL)end of life
    3.7 (EOL)end of life
    3.8 (EOL)end of life
    3.9 (EOL)end of life
    topic-ctypes
    type-bugAn unexpected behavior, bug, or error
    on May 23, 2020

  3. FRidh commented on May 23, 2020

    @FRidh
    FRidhmannequin
    on May 23, 2020
    MannequinAuthor

    I suppose this issue was not found yet because a) regression testing is done with ubuntu 18.04 LTS which uses binutils 2.30 and b) it, along with most distro's, will use ldconfig, which we in Nixpkgs have patched out.

  4. ezio-melotti
    transferred this issue fromon Apr 10, 2022
  5. serhiy-storchaka
    added this to Ctypes issueson Jan 1, 2024

  6. encukou commented on Feb 23, 2026

    @encukou
    encukou
    on Feb 23, 2026
    Member

    I'm proposing to soft-deprecate ctypes.util.find_library: https://discuss.python.org/t/106232

  7. encukou commented on Mar 20, 2026

    @encukou
    encukou
    on Mar 20, 2026
    Member

    It is now soft-deprecated. It cannot be made to work correctly and consistently on all platforms, and any change runs a chance to break whatever workarounds people already have in place.
    I'm prioritizing stability over new features, and encourage solving this outside ctypes itself.

    Also, find_library is now documented to depend on ldconfig and such.

  8. encukou
    closed this as not plannedon Mar 20, 2026
  9. github-project-automation
    moved this to Done in Ctypes issueson Mar 20, 2026
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