When using Apple Clang, --with-lto builds should not check for llvm-ar

[acmorrow]

BPO	43109
Nosy	@ronaldoussoren, @vstinner, @ned-deily, @miss-islington, @xrisk, @acmorrow
PRs	bpo-43109: Use /usr/bin/ar on macOS for LTO builds #25999 bpo-43109: Fix --with-lto configure option on macOS #26341 [3.10] bpo-43109: Fix --with-lto configure option on macOS (GH-26341) #26342 [3.9] bpo-43109: Fix --with-lto configure option on macOS (GH-26341) #26343 bpo-43109: configure doc: LTO requires "ar" on macOS #26349 [3.10] bpo-43109: configure doc: LTO requires "ar" on macOS (GH-26349) #26350

^{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/ned-deily'
closed_at = <Date 2021-05-25.10:58:37.915>
created_at = <Date 2021-02-02.22:52:49.269>
labels = ['OS-mac', 'build', '3.9', '3.10', '3.11', 'type-feature']
title = 'When using Apple Clang, --with-lto builds should not check for llvm-ar'
updated_at = <Date 2021-05-25.10:58:37.914>
user = 'https://github.com/acmorrow'

bugs.python.org fields:

activity = <Date 2021-05-25.10:58:37.914>
actor = 'vstinner'
assignee = 'ned.deily'
closed = True
closed_date = <Date 2021-05-25.10:58:37.915>
closer = 'vstinner'
components = ['Build', 'macOS']
creation = <Date 2021-02-02.22:52:49.269>
creator = 'acmorrow'
dependencies = []
files = []
hgrepos = []
issue_num = 43109
keywords = ['patch']
message_count = 6.0
messages = ['386174', '393334', '394291', '394292', '394323', '394324']
nosy_count = 6.0
nosy_names = ['ronaldoussoren', 'vstinner', 'ned.deily', 'miss-islington', 'xrisk', 'acmorrow']
pr_nums = ['25999', '26341', '26342', '26343', '26349', '26350']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43109'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[acmorrow]

When building with --with-lto, an explicit check for llvm-ar is performed as part of the configure step. However, Apple does not ship llvm-ar as part of Xcode, so when building with Apple Clang this check fails and prevents using --with-lto.

However, using the builtin ar seems to work just fine, and it can be selected by passing LLVM_AR=/path/to/ar to configure. It would be nice to see the configure script updated to know that system ar is sufficient when using Apple Clang on macOS.

Please see Homebrew/homebrew-core#70177 for additional background.

[ned-deily]

Thanks for the PR. I am looking at this area currently.

[miss-islington]

New changeset 25a9cf1 by Miss Islington (bot) in branch '3.10':
bpo-43109: Fix --with-lto configure option on macOS (GH-26341)
25a9cf1

[ned-deily]

New changeset 3af61a7 by Miss Islington (bot) in branch '3.9':
bpo-43109: Fix --with-lto configure option on macOS (GH-26341) (GH-26343)
3af61a7

[miss-islington]

New changeset ddc503c by Miss Islington (bot) in branch '3.10':
bpo-43109: configure doc: LTO requires "ar" on macOS (GH-26349)
ddc503c

[vstinner]

Thanks to the bug report Andrew C. Morrow, it's now fixed.

Commits in main:

commit 59acfd4
Author: Ned Deily <nad@python.org>
Date: Mon May 24 23:00:04 2021 -0400

bpo-43109: Fix --with-lto configure option on macOS (GH-26341)

Allow --with-lto configure option to work with Apple-supplied Xcode or
Command Line Tools which do not provide llvm-ar.

commit 63f17c2 (HEAD -> main, upstream/main)
Author: Victor Stinner <vstinner@python.org>
Date: Tue May 25 12:25:22 2021 +0200

bpo-43109: configure doc: LTO requires "ar" on macOS (GH-26349)

Commits in 3.10 branch:

commit ddc503c (upstream/3.10, 3.10)
Author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Tue May 25 03:56:37 2021 -0700

bpo-43109: configure doc: LTO requires "ar" on macOS (GH-26349)

(cherry picked from commit 63f17c252ab1b9357c5f022296213c42d9629458)

Co-authored-by: Victor Stinner <vstinner@python.org>