clang: a C language family frontend for LLVM

The goal of the Clang project is to create a new C, C++, Objective C and Objective C++ front-end for the LLVM compiler.

Features and Goals

Some of the goals for the project include the following:

• Real-world, production quality compiler.
• A single unified parser for C, Objective C, C++, and Objective C++.
• Language conformance with these languages and their variants, like C90, C99, etc.
• GCC compatibility: support GCC extensions, but allow them to be disabled.
• High performance and low memory use.
• Support many clients such as refactoring, static analysis, as well as code generation.
• Build a library-based architecture with finely crafted APIs, allowing the code to be reused in many ways.
• Design for integration with IDEs as well as code generation with the LLVM Optimizer and Code Generator.
• Expressive diagnostics: warnings and errors that are actually helpful and make sense.
• Use the LLVM 'BSD' License.
• Finally, make the code clean and simple enough to make it understandable to anyone who knows the languages involved and has a basic idea of compilers work.

Of course this is only a rough outline of the goals and features of Clang. To get a true sense of what it is all about, see the Features section. The Features section breaks each of these down and explains them in more detail.

Why?

The development of a new front-end was started out of a need -- a need for a compiler that allows better diagnostics, better integration with IDEs, a license that is compatible with commercial products, and a nimble compiler that is easy to develop and maintain. All of these were motivations for starting work on a new front-end that could meet these needs.

A good (but quite dated) introduction to Clang can be found in the following video lectures:

• Clang Introduction (May 2007)
• Features and Performance of Clang (July 2007)

For a more detailed comparison between Clang and other compilers, please see the clang comparison page.

Current Status

Clang is still in early development stages. If you are looking for source analysis or source-to-source transformation tools, clang is probably a great solution for you. If you want to use it as a drop in C compiler, it is not yet ready.

Clang currently has pretty good parsing and semantic analysis support for C and Objective-C right now, and bugs are usually quickly fixed once reported. C++ support is still very early, and we don't expect to have respectable C++ support for another 2 years or so.

Get Involved

The developers of Clang include contributers from Apple and numerous other volunteers. If you are interested in joining the community or learning more, please consider joining the cfe-dev mailing list, or start by browsing its archives.

If you are interested in trying out Clang, please see the build instructions on the Get Involved page.