mirror of
https://github.com/mollyim/webrtc.git
synced 2025-05-19 00:27:51 +01:00
4b97928b30
Allow to use AnyInvocable in webrtc. Demonstrate how AnyInvocable can make interface clearer to read and implement Demonstrate that AnyInvocable can reduce binary size Bug: None Change-Id: I33cf33fac6ed3bf4c5e46077d1cd984ca0f253a3 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/267165 Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Reviewed-by: Harald Alvestrand <hta@webrtc.org> Cr-Commit-Position: refs/heads/main@{#37380}
83 lines
2.8 KiB
Markdown
83 lines
2.8 KiB
Markdown
# Using Abseil in WebRTC
|
|
|
|
<?% config.freshness.owner = 'danilchap' %?>
|
|
<?% config.freshness.reviewed = '2021-05-12' %?>
|
|
|
|
You may use a subset of the utilities provided by the [Abseil][abseil]
|
|
library when writing WebRTC C++ code. Below, we list the explicitly
|
|
*allowed* and the explicitly *disallowed* subsets of Abseil; if you
|
|
find yourself in need of something that isn’t in either subset,
|
|
please add it to the *allowed* subset in this doc in the same CL that
|
|
adds the first use.
|
|
|
|
[abseil]: https://abseil.io/about/
|
|
|
|
|
|
## How to depend on Abseil
|
|
|
|
For build targets of type `rtc_library`, `rtc_source_set` and
|
|
`rtc_static_library`, dependencies on Abseil need to be listed in `absl_deps`
|
|
instead of `deps`.
|
|
|
|
This is needed in order to support the Abseil component build in Chromium. In
|
|
that build mode, WebRTC will depend on a monolithic Abseil build target that
|
|
will generate a shared library.
|
|
|
|
## **Allowed**
|
|
|
|
* `absl::AnyInvocable`
|
|
* `absl::bind_front`
|
|
* `absl::Cleanup`
|
|
* `absl::InlinedVector`
|
|
* `absl::WrapUnique`
|
|
* `absl::optional` and related stuff from `absl/types/optional.h`.
|
|
* `absl::string_view`
|
|
* The functions in `absl/strings/ascii.h`, `absl/strings/match.h`,
|
|
and `absl/strings/str_replace.h`.
|
|
* `absl::is_trivially_copy_constructible`,
|
|
`absl::is_trivially_copy_assignable`, and
|
|
`absl::is_trivially_destructible` from `absl/meta/type_traits.h`.
|
|
* `absl::variant` and related stuff from `absl/types/variant.h`.
|
|
* The functions in `absl/algorithm/algorithm.h` and
|
|
`absl/algorithm/container.h`.
|
|
* `absl/base/const_init.h` for mutex initialization.
|
|
* The macros in `absl/base/attributes.h`, `absl/base/config.h` and
|
|
`absl/base/macros.h`.
|
|
* `absl/numeric/bits.h`
|
|
|
|
|
|
## **Disallowed**
|
|
|
|
### `absl::make_unique`
|
|
|
|
*Use `std::make_unique` instead.*
|
|
|
|
### `absl::Mutex`
|
|
|
|
*Use `webrtc::Mutex` instead.*
|
|
|
|
Chromium has a ban on new static initializers, and `absl::Mutex` uses
|
|
one. To make `absl::Mutex` available, we would need to nicely ask the
|
|
Abseil team to remove that initializer (like they already did for a
|
|
spinlock initializer). Additionally, `absl::Mutex` handles time in a
|
|
way that may not be compatible with the rest of WebRTC.
|
|
|
|
### `absl::Span`
|
|
|
|
*Use `rtc::ArrayView` instead.*
|
|
|
|
`absl::Span` differs from `rtc::ArrayView` on several points, and both
|
|
of them differ from the `std::span` that was voted into
|
|
C++20—and `std::span` is likely to undergo further changes
|
|
before C++20 is finalized. We should just keep using `rtc::ArrayView`
|
|
and avoid `absl::Span` until C++20 is finalized and the Abseil team
|
|
has decided if they will change `absl::Span` to match.
|
|
[Bug](https://bugs.webrtc.org/9214).
|
|
|
|
### `absl::StrCat`, `absl::StrAppend`, `absl::StrJoin`, `absl::StrSplit`
|
|
|
|
*Use `rtc::SimpleStringBuilder` to build strings.*
|
|
|
|
These are optimized for speed, not binary size. Even `StrCat` calls
|
|
with a modest number of arguments can easily add several hundred bytes
|
|
to the binary.
|