| # Using Abseil in WebRTC |
| |
| 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/ |
| |
| ## **Allowed** |
| |
| * `absl::InlinedVector` |
| * `absl::make_unique` and `absl::WrapUnique` |
| * `absl::optional` and related stuff from `absl/types/optional.h`. |
| * `absl::string_view` |
| * `absl::variant` and related stuff from `absl/types/variant.h`. |
| |
| ## **Disallowed** |
| |
| ### `absl::Mutex` |
| |
| *Use `rtc::CriticalSection` 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 compaible 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` and `absl::StrAppend` |
| |
| *Use `rtc::SimpleStringBuilder` instead.* |
| |
| 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. |
