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1=======================2Extended C++03 Support3=======================4 5.. contents::6 :local:7 8Overview9========10 11libc++ is an implementation of the C++ standard library targeting C++11 or later.12 13In C++03, the library implements the C++11 standard using C++11 language extensions provided14by Clang.15 16This document tracks the C++11 extensions libc++ requires, the C++11 extensions it provides,17and how to write minimal C++11 inside libc++.18 19Required C++11 Compiler Extensions20==================================21 22Clang provides a large subset of C++11 in C++03 as an extension. The features23libc++ expects Clang to provide are:24 25* Variadic templates.26* RValue references and perfect forwarding.27* Alias templates28* defaulted and deleted Functions.29* reference qualified Functions30* ``auto``31 32There are also features that Clang *does not* provide as an extension in C++0333mode. These include:34 35* ``constexpr`` and ``noexcept``36* Trailing return types.37* ``>>`` without a space.38 39 40Provided C++11 Library Extensions41=================================42 43.. warning::44 The C++11 extensions libc++ provides in C++03 are currently undergoing change. Existing extensions45 may be removed in the future. New users are strongly discouraged depending on these extension46 in new code.47 48 This section will be updated once the libc++ developer community has further discussed the49 future of C++03 with libc++.50