======================= Extended C++03 Support

.. contents:: :local:

Overview

libc++ is an implementation of the C++ standard library targeting C++11 or later.

In C++03, the library implements the C++11 standard using C++11 language extensions provided by Clang.

This document tracks the C++11 extensions libc++ requires, the C++11 extensions it provides, and how to write minimal C++11 inside libc++.

Required C++11 Compiler Extensions

Clang provides a large subset of C++11 in C++03 as an extension. The features libc++ expects Clang to provide are:

• Variadic templates.
• RValue references and perfect forwarding.
• Alias templates
• defaulted and deleted Functions.
• reference qualified Functions
• auto

There are also features that Clang does not provide as an extension in C++03 mode. These include:

• constexpr and noexcept
• Trailing return types.
• >> without a space.

Provided C++11 Library Extensions

.. warning:: The C++11 extensions libc++ provides in C++03 are currently undergoing change. Existing extensions may be removed in the future. New users are strongly discouraged depending on these extension in new code.

This section will be updated once the libc++ developer community has further discussed the future of C++03 with libc++.