dependencies: add custom atomic dependency by Dudemanguy · Pull Request #11445 · mesonbuild/meson

Dudemanguy · 2023-02-23T16:17:37Z

Almost exactly the same as how the dl dependency works. On certain systems (like BSDs that use clang), stdatomic is provided by compiler-rt and doesn't need a separate library explictly linked. On a typical GNU/LINUX system, atomic is a separate library that must be explictly found and linked against. So just add a builtin and system method for these two use cases.

codecov · 2023-02-23T16:30:52Z

Codecov Report

Merging #11445 (231ab94) into master (eb472a1) will increase coverage by 3.44%.
The diff coverage is n/a.

❗ Current head 231ab94 differs from pull request most recent head 4a56692. Consider uploading reports for the commit 4a56692 to get more accurate results

@@            Coverage Diff             @@
##           master   #11445      +/-   ##
==========================================
+ Coverage   65.25%   68.70%   +3.44%     
==========================================
  Files         420      209     -211     
  Lines       91410    45429   -45981     
  Branches    20305     9402   -10903     
==========================================
- Hits        59648    31211   -28437     
+ Misses      27115    11817   -15298     
+ Partials     4647     2401    -2246

see 273 files with indirect coverage changes

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jscott0 · 2023-03-26T15:25:08Z

I'm not qualified to review this, but it's been a long time since atomics were merged into the C standard, and since POSIX hasn't yet addressed the issue, I very much welcome Meson's support for an atomic dependency

thesamesam · 2023-03-29T23:35:55Z

The discussion in #10621 is relevant. I need to look at this more later though, we've run into a series of issues on odd platforms with atomic tests.

Dudemanguy · 2023-03-30T00:23:21Z

The intention is indeed to first check if atomics is already provided and if not try to link the atomic library if possible. I confess that I do not know if atomics are more complicated than that.

Dudemanguy · 2023-04-11T03:31:01Z

I bumped it to 1.2.0 now.

Dudemanguy · 2023-07-24T06:20:45Z

Updated to 1.3.0 now.

eli-schwartz · 2024-06-23T15:24:59Z

mesonbuild/dependencies/misc.py

+    'atomic',
+    [DependencyMethods.BUILTIN, DependencyMethods.SYSTEM],
+    builtin_class=AtomicBuiltinDependency,
+    system_class=AtomicSystemDependency,


This has come up in Gentoo before, which also had a test to add -latomic to LDFLAGS after running some test code to see if it's necessary for a successful link.

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=ec90f4c3a4e0ef9841dede7b18df90e2aceafd45

We (I, actually) disabled that and replaced it with some code that says "is -latomic a valid library? Good, then use it unconditionally with -Wl,--push-state,--as-needed,-latomic,--pop-state". The reason was that the test often misfired because the test code could be satisfied via builtins, but more advanced use cases in the software being built required explicit -latomic.

So I wonder if maybe we really need to first check DependencyMethods.SYSTEM, on the same assumption: if -latomic is a valid external library, adding it to be cautious is assumed to never be harmful. It makes the compiler command line potentially longer and the linker has to add another library to search through for available symbols, but that's not a huge problem given the alternative.

Sure, that sounds reasonable to me. I swapped the order so the system method is checked first.

thesamesam · 2024-12-27T07:03:32Z

docs/markdown/Dependencies.md

+
+Provides access to the atomic operations library. This first attempts
+to look for a valid atomic external library before trying to fallback
+to what is provided by the libc.


Suggested change

to what is provided by the libc.

to what is provided by the C runtime libraries.

but let's fix that on merge to avoid delaying this more.

Well, since we forgot to re-review this a while back we do need to bump the new-since version number yet again... :)

Other than that though I do think this looks quite reasonable.

eli-schwartz

This looks pretty good. Sorry for not reviewing it earlier. Minor formatting nits below but otherwise LGTM.

Needs the version number to be bumped up yet again to 1.7.0, I'm afraid. :(

eli-schwartz · 2024-12-27T07:09:15Z

mesonbuild/dependencies/misc.py



+class AtomicBuiltinDependency(BuiltinDependency):
+    def __init__(self, name: str, env: 'Environment', kwargs: T.Dict[str, T.Any]):


Nit: the codebase now depends on python 3.7 and as such, uses from __future__ import annotations everywhere. That means we don't need to quote annotations to defer them anymore. We should use the new style, i.e. avoid the quotes, when adding brand-new code

eli-schwartz · 2024-12-27T07:09:30Z

mesonbuild/dependencies/misc.py

+
+
+class AtomicSystemDependency(SystemDependency):
+    def __init__(self, name: str, env: 'Environment', kwargs: T.Dict[str, T.Any]):


(and same here)

Almost exactly the same as how the dl dependency works. On certain systems (like BSDs that use clang), stdatomic is provided by compiler-rt and doesn't need a separate library explictly linked. On a typical GNU/LINUX system, atomic is a separate library that must be explictly found and linked against. So just add a builtin and system method for these two use cases.

Dudemanguy · 2024-12-27T20:55:38Z

Totally forgot about this PR as well. Rebased and updated.

eli-schwartz · 2024-12-27T21:39:56Z

Thanks for the rebase, will review on Sunday as I'm out of time today

neheb · 2025-06-30T05:11:13Z

@Dudemanguy

fails on NetBSD:

  The Meson build system
  Version: 1.7.0
  Source dir: /home/runner/work/libtorrent/libtorrent
  Build dir: /home/runner/work/libtorrent/libtorrent/build
  Build type: native build
  Project name: libtorrent
  Project version: 0.15.4
  C++ compiler for the host machine: c++ (gcc 10.5.0 "c++ (nb3 20231008) 10.5.0")
  C++ linker for the host machine: c++ ld.bfd 2.34
  Host machine cpu family: x86_64
  Host machine cpu: x86_64
  Compiler for C++ supports function attribute visibility:default: YES 
  Header "new" has symbol "std::hardware_constructive_interference_size" : NO 
  Checking for size of "void*" : 8 
  Has header "sys/epoll.h" : NO 
  Has header "sys/inotify.h" : NO 
  Header "sys/mman.h" has symbol "madvise" : YES 
  Header "sys/mman.h" has symbol "mincore" : YES 
  Checking for function "__builtin_popcount" : YES 
  Checking for function "posix_fadvise" : YES 
  Checking for function "fallocate" : NO 
  Checking for function "posix_fallocate" : YES 
  Has header "sys/statvfs.h" : YES 
  Library execinfo found: YES
  Checking for function "backtrace" : NO 
  Has header "sys/event.h" : YES 
  Run-time dependency atomic found: NO (tried system and builtin)
  
  meson.build:145:15: ERROR: Dependency "atomic" not found, tried system and builtin

edit: openbsd too.

thesamesam · 2025-06-30T05:20:16Z

Please file a new bug.

neheb · 2025-06-30T18:25:52Z

#14755

Dudemanguy requested a review from jpakkane as a code owner February 23, 2023 16:17

Dudemanguy force-pushed the stdatomic-dep branch from 484f5bb to 4a56692 Compare April 11, 2023 03:09

Dudemanguy force-pushed the stdatomic-dep branch from 4a56692 to 416c717 Compare July 24, 2023 06:20

Dudemanguy force-pushed the stdatomic-dep branch 2 times, most recently from 2007324 to fc07c2b Compare June 23, 2024 14:56

eli-schwartz reviewed Jun 23, 2024

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Dudemanguy force-pushed the stdatomic-dep branch from fc07c2b to 7c407ce Compare June 23, 2024 15:45

rgommers mentioned this pull request Jun 27, 2024

MAINT: use an atomic load/store and a mutex to initialize the argparse and runtime import caches numpy/numpy#26780

Merged

thesamesam approved these changes Dec 27, 2024

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eli-schwartz requested changes Dec 27, 2024

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Dudemanguy force-pushed the stdatomic-dep branch from 7c407ce to 9fd0695 Compare December 27, 2024 20:33

eli-schwartz approved these changes Dec 30, 2024

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eli-schwartz merged commit f070670 into mesonbuild:master Dec 30, 2024

Dudemanguy deleted the stdatomic-dep branch December 30, 2024 03:42

	to what is provided by the libc.
	to what is provided by the C runtime libraries.



		class AtomicBuiltinDependency(BuiltinDependency):
		def __init__(self, name: str, env: 'Environment', kwargs: T.Dict[str, T.Any]):



		class AtomicSystemDependency(SystemDependency):
		def __init__(self, name: str, env: 'Environment', kwargs: T.Dict[str, T.Any]):

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