Using Abseil in WebRTC

You may use a subset of the utilities provided by the 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.

How to depend on Abseil

Dependencies on Abseil need to be listed in deps using absolute path, for example "//third_party/abseil-cpp/absl/base:core_headers"

The rtc GN templates will take care of generating the proper dependency when used within Chromium or standalone. In the build_with_chromium mode, WebRTC will depend on the monolithic Abseil build target that will generate a shared library.

Allowed

  • absl::AnyInvocable

  • absl::bind_front

  • absl::Cleanup

  • Hash tables, and B-tree ordered containers

  • absl::InlinedVector

  • absl_nonnull and absl_nullable

  • absl::NoDestructor

  • absl::WrapUnique

  • absl::string_view (preferred over std::string_view, see issue 42225436 for details)

  • The functions in absl/strings/ascii.h, absl/strings/match.h, and absl/strings/str_replace.h.

  • The functions in absl/strings/escaping.h.

  • The functions in absl/algorithm/algorithm.h and absl/algorithm/container.h.

  • The macros in absl/base/attributes.h, absl/base/config.h and absl/base/macros.h.

  • absl/numeric/bits.h

  • absl/crc

  • Single argument absl::StrCat

  • ABSL_FLAG is allowed in tests and tools, but disallowed in in non-test code.

Disallowed

absl::make_unique

Use std::make_unique instead.

absl::Mutex

Use webrtc::Mutex instead.

absl::optional and absl::variant

Use std::optional and std::variant directly.

absl::Span

Use std::span instead.

absl::Span differs from std::span on several points, in particular lacks static extent template parameter that WebRTC relies on.

absl::StrCat, absl::StrAppend, absl::StrJoin, absl::StrSplit

Use webrtc::StringBuilder 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.

Exception: Single-argument absl::StrCat is allowed in order to make it easy to use AbslStringify. See TOTW #215 for details on AbslStringify.