Clang

Clang (ˈklæŋ) is a compiler front end for the C, C++, Objective-C, and Objective-C++ programming languages, as well as the OpenMP, OpenCL, RenderScript, CUDA, SYCL, and HIP frameworks. It acts as a drop-in replacement for the GNU Compiler Collection (GCC), supporting most of its compilation flags and unofficial language extensions. It includes a static analyzer, and several code analysis tools. Clang operates in tandem with the LLVM compiler back end and has been a subproject of LLVM 2.6 and later. As with LLVM, it is free and open-source software under the Apache License 2.0 software license. Its contributors include Apple, Microsoft, Google, ARM, Sony, Intel, and AMD. Clang 16, the latest major version of Clang as of June 2023, has full support for all published C++ standards up to C++17, implements most features of C++20, and has initial support for the upcoming C++23 standard. Since v16.0.0, Clang compiles C++ using the GNU++17 dialect by default, which includes features from the C++17 standard and conforming GNU extensions. Starting in 2005, Apple Inc. began extensive use of LLVM in several commercial products, including the iOS SDK and Xcode 3.1. One of the first uses of LLVM was an OpenGL code compiler for OS X that converts OpenGL calls into more fundamental calls for graphics processing units (GPU) that do not support certain features. This allowed Apple to support OpenGL on computers using Intel GMA chipsets, increasing performance on those machines. The LLVM project originally intended to use GCC's front end. The GCC source code, however, is large and somewhat cumbersome; as one long-time GCC developer put it referring to LLVM, "Trying to make the hippo dance is not really a lot of fun". Besides, Apple software uses Objective-C, which is a low priority for GCC developers. As such, GCC does not integrate smoothly into Apple's integrated development environment (IDE). Finally, GCC's license agreement, the GNU General Public License (GPL) version 3, requires developers who distribute extensions or modified versions of GCC to make their source code available, but LLVM's permissive software license doesn't require this.