WebRTC coding style guide

General advice

Some older parts of the code violate the style guide in various ways.

If making small changes to such code, follow the style guide when it’s reasonable to do so, but in matters of formatting etc., it is often better to be consistent with the surrounding code.
If making large changes to such code, consider first cleaning it up in a separate CL.

C++

WebRTC follows the Chromium and Google C++ style guides. In cases where they conflict, the Chromium style guide trumps the Google style guide, and the rules in this file trump them both.

ArrayView

When passing an array of values to a function, use rtc::ArrayView whenever possible—that is, whenever you’re not passing ownership of the array, and don’t allow the callee to change the array size.

For example,

instead of	use
`const std::vector<T>&`	`ArrayView<const T>`
`const T* ptr, size_t num_elements`	`ArrayView<const T>`
`T* ptr, size_t num_elements`	`ArrayView<T>`

See the source for more detailed docs.

C

There’s a substantial chunk of legacy C code in WebRTC, and a lot of it is old enough that it violates the parts of the C++ style guide that also applies to C (naming etc.) for the simple reason that it pre-dates the use of the current C++ style guide for this code base.

If making small changes to C code, mimic the style of the surrounding code.
If making large changes to C code, consider converting the whole thing to C++ first.

Java

WebRTC follows the Google Java style guide.

Objective-C and Objective-C++

WebRTC follows the Chromium Objective-C and Objective-C++ style guide.

Python

WebRTC follows Chromium’s Python style.

Build files

The WebRTC build files are written in GN, and we follow the Chromium GN style guide. Additionally, there are some WebRTC-specific rules below; in case of conflict, they trump the Chromium style guide.

WebRTC-specific GN templates

Use the following GN templates to ensure that all our targets are built with the same configuration:

instead of	use
`executable`	`rtc_executable`
`shared_library`	`rtc_shared_library`
`source_set`	`rtc_source_set`
`static_library`	`rtc_static_library`
`test`	`rtc_test`

Conditional compilation with the C preprocessor

Avoid using the C preprocessor to conditionally enable or disable pieces of code. But if you can’t avoid it, introduce a GN variable, and then set a preprocessor constant to either 0 or 1 in the build targets that need it:

if (apm_debug_dump) {
  defines = [ "WEBRTC_APM_DEBUG_DUMP=1" ]
} else {
  defines = [ "WEBRTC_APM_DEBUG_DUMP=0" ]
}

In the C, C++, or Objective-C files, use #if when testing the flag, not #ifdef or #if defined():

#if WEBRTC_APM_DEBUG_DUMP
// One way.
#else
// Or another.
#endif

When combined with the -Wundef compiler option, this produces compile time warnings if preprocessor symbols are misspelled, or used without corresponding build rules to set them.