Changes in atomic

bbd871e2baad2e74dbde202823b3439d2a96d3f8 - [libc++] Don't implement before C++23 (#123130)

Fri, 17 Jan 2025 19:22:40 +0000

[libc++] Don't implement before C++23 (#123130)https://github.com/llvm/llvm-project/pull/95498 implemented a libc++ extension where would forward to even before C++23. Unfortunately, this was found to be a breaking change (with fairly widespread impact) since that changes whether _Atomic(T) is a C style atomic or std::atomic. In principle, this can even be an ABI break. We generally don't implement extensions in libc++ because they cause so many problems, and that extension had been accepted because it was deemed pretty small and only a quality of life improvement. Since it has widespread impact on valid C++20 (and before) code, this patch removes the extension before we ship it in any public release. List of files: /llvm-project/libcxx/include/atomic

b9a2658a3e8bd13b0f9e7a8a440832a95b377216 - [libc++][C++03] Use `__cxx03/` headers in C++03 mode (#109002)

Sat, 21 Dec 2024 12:01:48 +0000

[libc++][C++03] Use `__cxx03/` headers in C++03 mode (#109002)This patch implements the forwarding to frozen C++03 headers asdiscussed inhttps://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc. In theRFC, we initially proposed selecting the right headers from the Clangdriver, however consensus seemed to steer towards handling this in thelibrary itself. This patch implements that direction.At a high level, the changes basically amount to making each publicheader look like this:```// inside #ifdef _LIBCPP_CXX03_LANG# include <__cxx03/vector>#else // normal content#endif```In most cases, public headers are simple umbrella headers so there isn'tmuch code in the #else branch. In other cases, the #else branch containsthe actual implementation of the header. List of files: /llvm-project/libcxx/include/atomic

c166a9c713ec86b86f1f178a5133bc128fd0a610 - [libc++] Add #if 0 block to all the top-level headers (#119234)

Tue, 10 Dec 2024 15:02:12 +0000

[libc++] Add #if 0 block to all the top-level headers (#119234)Including The frozen C++03 headers results in a lot of formattingchanges in the main headers, so this splits these changes into aseparate commit instead.This is part ofhttps://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc. List of files: /llvm-project/libcxx/include/atomic

0e34f3f4968d8d32a64e26777541f939deb2274c - [libc++] Extract a clean base support API for std::atomic (#118129)

Mon, 09 Dec 2024 14:14:17 +0000

[libc++] Extract a clean base support API for std::atomic (#118129)This patch documents the underlying API for implementing atomics on a platform. This doesn't change the operations that std::atomic is based on, but it reorganizes the C11 / GCC implementation split to make it clearer what's the base support layer and what's not. List of files: /llvm-project/libcxx/include/atomic

3a63407686313f46f9abc664fd10b01f4359ee27 - [libc++] Make __atomic_base into an implementation detail of std::atomic (#115764)

Tue, 19 Nov 2024 23:35:14 +0000

[libc++] Make __atomic_base into an implementation detail of std::atomic (#115764)The __atomic_base base class is only useful to conditionalize the operations we provide inside std::atomic. It shouldn't be used directly from other places in the library which can use std::atomic directly instead. Since we've granularized our includes, using std::atomic directly should not make much of a difference compile-time wise. This patch starts using std::atomic directly from other classes like std::barrier and std::latch. Changing this shouldn't be an ABI break since both classes have the same size and layout. The benefits of this patch are isolating other parts of the code base from implementation details of std::atomic and simplifying the mental model for std::atomic's layers of implementation by making it clear that __atomic_base is only an implementation detail of std::atomic. List of files: /llvm-project/libcxx/include/atomic

e99c4906e44ae3f921fa05356909d006cda8d954 - [libc++] Granularize includes (#108696)

Thu, 31 Oct 2024 01:20:10 +0000

[libc++] Granularize includes (#108696) List of files: /llvm-project/libcxx/include/atomic

ba87515fea90b5d55836a8e3be63a7e683ce299d - [libc++][RFC] Always define internal feature test macros (#89178)

Sat, 12 Oct 2024 07:49:52 +0000

[libc++][RFC] Always define internal feature test macros (#89178)Currently, the library-internal feature test macros are only defined if the feature is not available, and always have the prefix `_LIBCPP_HAS_NO_`. This patch changes that, so that they are always defined and have the prefix `_LIBCPP_HAS_` instead. This changes the canonical use of these macros to `#if _LIBCPP_HAS_FEATURE`, which means that using an undefined macro (e.g. due to a missing include) is diagnosed now. While this is rather unlikely currently, a similar change in `<__configuration/availability.h>` caught a few bugs. This also improves readability, since it removes the double-negation of `#ifndef _LIBCPP_HAS_NO_FEATURE`. The current patch only touches the macros defined in `<__config>`. If people are happy with this approach, I'll make a follow-up PR to also change the macros defined in `<__config_site>`. List of files: /llvm-project/libcxx/include/atomic

2d26fc8c6c5015b77dc725695c1d957f412e4141 - [libc++] Enable C++ stdatomic.h for all C++ versions (#95498)

Thu, 19 Sep 2024 13:43:54 +0000

[libc++] Enable C++ stdatomic.h for all C++ versions (#95498)This extension is motivated by Android's use of libc++, where has redirected to for many years, long before it was standardized in C++23. When libc++'s stdatomic.h is included in C translation units, delegate to the next stdatomic.h, which could come from Clang or libc. List of files: /llvm-project/libcxx/include/atomic

bf1666fb0bc19ffa18072e2727e4611c293a9aee - [libc++] Drop support for the C++20 Synchronization Library before C++20 (#82008)

Wed, 31 Jul 2024 21:53:09 +0000

[libc++] Drop support for the C++20 Synchronization Library before C++20 (#82008)When we initially implemented the C++20 synchronization library, we reluctantly accepted for the implementation to be backported to C++03 upon request from the person who provided the patch. This was when we were only starting to have experience with the issues this can create, so we flinched. Nowadays, we have a much stricter stance about not backporting features to previous standards. We have recently started fixing several bugs (and near bugs) in our implementation of the synchronization library. A recurring theme during these reviews has been how difficult to understand the current code is, and upon inspection it becomes clear that being able to use a few recent C++ features (in particular lambdas) would help a great deal. The code would still be pretty intricate, but it would be a lot easier to reason about the flow of callbacks through things like __thread_poll_with_backoff. As a result, this patch drops support for the synchronization library before C++20. This makes us more strictly conforming and opens the door to major simplifications, in particular around atomic_wait which was supported all the way to C++03. This change will probably have some impact on downstream users, however since the C++20 synchronization library was added only in LLVM 10 (~3 years ago) and it's quite a niche feature, the set of people trying to use this part of the library before C++20 should be reasonably small. List of files: /llvm-project/libcxx/include/atomic

dfddc0c4843baaf9605aeb1c4f82eac185e90265 - [libc++] Include the rest of the detail headers by version in the umbrella headers (#96032)

Thu, 18 Jul 2024 08:59:58 +0000

[libc++] Include the rest of the detail headers by version in the umbrella headers (#96032)This is a follow-up to #83740. List of files: /llvm-project/libcxx/include/atomic

42ba740afffa16f991be6aa36626bd872d41ebc0 - [libc++] Implement C++20 atomic_ref (#76647)

Tue, 21 May 2024 22:54:08 +0000

[libc++] Implement C++20 atomic_ref (#76647)Implement the std::atomic_ref class template by reusing atomic_base_impl. Based on the work from https://reviews.llvm.org/D72240 List of files: /llvm-project/libcxx/include/atomic

40081a45a14f7aa6249fa034d961549c0b1762a0 - [libc++] Fix diagnostic for before C++23 (#83351)

Mon, 04 Mar 2024 23:24:51 +0000

[libc++] Fix diagnostic for before C++23 (#83351)We normally try to issue a reasonable diagnostic when mixing and before C++23. However, after granularizing the header, the check and the #error message was moved to *after* the point where mixing both causes problems. When mixing both headers, we would hence get the diagnostic burried under a pile of previous diagnostics in e.g. __atomic/kill_dependency.h. This patch moves the check earlier to restore the intended behavior. It also switches from `#ifdef kill_dependency` to an explicit check of the inclusion of the header and the Standard version, which seems to be more reliable than checking whether a macro is defined. List of files: /llvm-project/libcxx/include/atomic

37dca605c9bd41732da010ee97ed15ad9585a37d - [libc++] Clean up includes of <__assert> (#80091)

Thu, 29 Feb 2024 15:12:22 +0000

[libc++] Clean up includes of <__assert> (#80091)Originally, we used __libcpp_verbose_abort to handle assertion failures. That function was declared from all public headers. Since we don't use that mechanism anymore, we don't need to declare __libcpp_verbose_abort from all public headers, and we can clean up a lot of unnecessary includes. This patch also moves the definition of the various assertion categories to the <__assert> header, since we now rely on regular IWYU for these assertion macros. rdar://105510916 List of files: /llvm-project/libcxx/include/atomic

153003416696c2464d296594dac5a36a5a60bac5 - [libc++] Remove unnecessary includes from (#82880)

Wed, 28 Feb 2024 20:14:35 +0000

[libc++] Remove unnecessary includes from (#82880)This reduces the include time of `` from 135ms to 88ms. List of files: /llvm-project/libcxx/include/atomic

6f0c52e56fb7f237ed8071573ce8a2021b4c7289 - [libc++] Refactor atomic_{unsigned,signed}_lock_free (#73041)

Wed, 22 Nov 2023 19:54:40 +0000

[libc++] Refactor atomic_{unsigned,signed}_lock_free (#73041)Their definition was a bit roundabout and it was actually wrong since atomic_unsigned_lock_free would be a signed type whenever __cxx_contention_t is lock free, which is most of the time. Fixes #72968 List of files: /llvm-project/libcxx/include/atomic

de7fbfeef5984ed3dc178957fbfaf4b1bb95fa94 - [libc++] Floating Point Atomic (#67799)

Wed, 22 Nov 2023 11:48:49 +0000

[libc++] Floating Point Atomic (#67799)- implement P0020R6 Floating Point Atomic Differential Revision: https://reviews.llvm.org/D153981 List of files: /llvm-project/libcxx/include/atomic

70617a1a2389a1abe6151d52dc749fb5f7755439 - [libc++] Granularize includes

Tue, 31 Jan 2023 18:23:30 +0000

[libc++] Granularize includesReviewed By: ldionne, Mordante, #libcSpies: arichardson, libcxx-commitsDifferential Revision: https://reviews.llvm.org/D144255 List of files: /llvm-project/libcxx/include/atomic

46db8d822ecdf36a714de5e1acf187736a3af5d1 - [libc++] Granularize

Sat, 14 Jan 2023 01:53:52 +0000

[libc++] Granularize Reviewed By: Mordante, #libcSpies: arichardson, libcxx-commits, krytarowskiDifferential Revision: https://reviews.llvm.org/D142972 List of files: /llvm-project/libcxx/include/atomic

4f15267d3dd797a15901fe9352f0d5fa121b9095 - [libc++][NFC] Replace _LIBCPP_STD_VER > x with _LIBCPP_STD_VER >= x

Mon, 13 Feb 2023 23:56:09 +0000

[libc++][NFC] Replace _LIBCPP_STD_VER > x with _LIBCPP_STD_VER >= xThis change is almost fully mechanical. The only interesting change is in `generate_feature_test_macro_components.py` to generate `_LIBCPP_STD_VER >=` instead. To avoid churn in the git-blame this commit should be added to the `.git-blame-ignore-revs` once committed.Reviewed By: ldionne, var-const, #libcSpies: jloser, libcxx-commits, arichardson, arphaman, wenleiDifferential Revision: https://reviews.llvm.org/D143962 List of files: /llvm-project/libcxx/include/atomic

dc21ce44047a634ee9072157b6dc40926f02458a - [libc++] Remove includes from and

Sun, 15 Jan 2023 18:53:49 +0000

[libc++] Remove includes from and Reviewed By: Mordante, #libcSpies: libcxx-commitsDifferential Revision: https://reviews.llvm.org/D141799 List of files: /llvm-project/libcxx/include/atomic