04ab497275
Remove mention of absl_deps - it is history already. Rewrite motiviation of banning absl::Span to be up to date with c++20 state. Remove motivation of banning absl::Mutex as it likely no longer accurate, and that ban might be re-evaluated. Ensure allow list matches what is in root DEPS No-Try: True Bug: b/363943024, webrtc:342905193 Change-Id: I890a87511bafac7c51355d8f49e0237352eee7b9 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/361302 Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Reviewed-by: Harald Alvestrand <hta@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/main@{#42914}
81 lines
2.5 KiB
Markdown
81 lines
2.5 KiB
Markdown
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<!--* freshness: {owner: 'danilchap' reviewed: '2024-09-02'} *-->
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# Using Abseil in WebRTC
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You may use a subset of the utilities provided by the [Abseil][abseil]
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library when writing WebRTC C++ code. Below, we list the explicitly
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*allowed* and the explicitly *disallowed* subsets of Abseil; if you
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find yourself in need of something that isn’t in either subset,
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please add it to the *allowed* subset in this doc in the same CL that
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adds the first use.
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[abseil]: https://abseil.io/about/
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## How to depend on Abseil
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For build targets of type `rtc_library`, `rtc_source_set` and
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`rtc_static_library`, dependencies on Abseil need to be listed in `deps`.
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The GN templates will take care of generating the proper dependency when
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used within Chromium or standalone. In that build mode, WebRTC will depend
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on a monolithic Abseil build target that will generate a shared library.
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## **Allowed**
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* `absl::AnyInvocable`
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* `absl::bind_front`
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* `absl::Cleanup`
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* `absl::InlinedVector`
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* `absl::Nonnull` and `absl::Nullable`
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* `absl::WrapUnique`
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* `absl::string_view`
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* The functions in `absl/strings/ascii.h`, `absl/strings/match.h`,
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and `absl/strings/str_replace.h`.
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* The functions in `absl/strings/escaping.h`.
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* `absl::is_trivially_copy_constructible`,
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`absl::is_trivially_copy_assignable`, and
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`absl::is_trivially_destructible` from `absl/meta/type_traits.h`.
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* `absl::variant` and related stuff from `absl/types/variant.h`.
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* The functions in `absl/algorithm/algorithm.h` and
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`absl/algorithm/container.h`.
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* `absl/base/const_init.h` for mutex initialization.
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* The macros in `absl/base/attributes.h`, `absl/base/config.h` and
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`absl/base/macros.h`.
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* `absl/numeric/bits.h`
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* ABSL_FLAG is allowed in tests and tools, but disallowed in in non-test code.
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## **Disallowed**
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### `absl::make_unique`
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*Use `std::make_unique` instead.*
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### `absl::Mutex`
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*Use `webrtc::Mutex` instead.*
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### `absl::optional`
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*Use `std::optional` instead.*
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### `absl::Span`
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*Use `rtc::ArrayView` instead.*
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`absl::Span` differs from `rtc::ArrayView` on several points, and both
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of them differ from the `std::span` introduced in C++20. We should just keep
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using `rtc::ArrayView` and avoid `absl::Span`. When WebRTC switches to C++20,
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we will consider replacing `rtc::ArrayView` with `std::span`.
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### `absl::StrCat`, `absl::StrAppend`, `absl::StrJoin`, `absl::StrSplit`
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*Use `rtc::SimpleStringBuilder` to build strings.*
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These are optimized for speed, not binary size. Even `StrCat` calls
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with a modest number of arguments can easily add several hundred bytes
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to the binary.
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