C++ Reference

This page is a grab bag of useful links to C++ documentation in the Mozilla source docs or in the source code itself.

This will grow and gain organisation, so please add any links you find useful!

Miscellaneous

• Using C++ in Mozilla code - general C++ coding guidelines.

• XPIDL - details for XPCOM IDL files (e.g. how the types map between IDL, C++, Rust and JS).

• {fmt} in Gecko - An implementation of C++20’s std::format formatting API, with some extra Mozilla goodies.

• GTests - Unit tests for C++.

Data structures

• String Guide - nsString vs nsCString vs nsACString et al.

• C++ and Mozilla standard libraries - Guidelines for using standard C++ containers and libraries.

• nsTArray - Analogous to std::vector.

• HashMap and HashSet, both built on top of HashTable (examples in GTest). Probably prefer these to nsTHashMap/nsTHashSet, which use a lot more virtual calls and less templating/inlining.

• Span - A Slice type for C++ (examples in GTest).

Utility

• Result - Analogous to Rust Result<> (examples in GTest).

• Maybe - Analogous to Rust Option<> or C++ std::optional (examples in GTest).

• ScopeExit - An RAII guard to automatically handle scoped cleanup.

• MozPromise - Promises for C++.