How Clang/LLVM empowers the underhood of the Android build system​

How Clang/LLVM empowers the underhood of the Android build system​

When it comes to compiling code for Android development, developers have a choice between two popular compiler infrastructures: GCC and Clang/LLVM. Each has unique advantages and disadvantages, and being aware of these can help developers choose wisely for their Android projects. In the following sections, we’ll look at their features and weigh their advantages and disadvantages with a special focus on how CLang/LLVM fit the Android build system.

GCC: A Trusted Workhorse

With its long history and wide range of language support, GCC (GNU Compiler Collection) has been the go-to compiler for many years. It offers maturity and a robust feature set, making it suitable for various development scenarios. Android developers who choose GCC can benefit from its performance optimizations, resulting in fast and efficient code execution. Additionally, GCC’s support for multiple programming languages, including C, C++, Objective-C, Fortran, and Ada, allows developers to work with diverse codebases.

However, GCC does have some drawbacks. Its error messages and warnings can be less clear and user-friendly compared to Clang/LLVM. Compilation speed can also be a concern, as GCC may take longer to compile code, especially for larger projects. Additionally, GCC’s memory usage during compilation can be higher, which can be a consideration for resource-constrained environments.

Clang/LLVM: The Modern and Modular Choice

CLang is a compiler front-end for C, C++, Objective-C, Objective-C++ and some other languages supporting most of the GCC flags. Having a static analyzer and some other code analysis tools enables developers to detect probable bugs during compilation and get rid of these issues. LLVM stands for Low-Level Virtual Machine which is a collection of reusable compiler and toolchain technologies. They have gained popularity in recent years, particularly in the Android ecosystem. Clang, as the front-end compiler, offers user-friendly diagnostics with clear error messages and warnings that can significantly improve the developer experience, making it easier to identify and fix issues in the code. Furthermore, Clang’s fast compilation speed is advantageous for iterative development and can lead to shorter build times.

The LLVM infrastructure’s modular structure allows for the incorporation of new tools and technologies, making it extremely flexible to a variety of development needs.

Android Usage

There has been a noticeable trend towards Clang/LLVM as the default compiler in the Android Open Source Project (AOSP). The Android platform will perform better as a result of Clang’s integration thanks to better optimizations and a smaller memory footprint. Better diagnostics, quicker compilation times, and support for current C++ features have all contributed to the switch from GCC to Clang/LLVM.

While most AOSP and pre-installed system apps are built using Clang/LLVM, some parts that are closely related to the Linux kernel, which still uses GCC, are still built using GCC. This hybrid strategy guarantees compatibility and makes use of both compilers’ advantages.


  1. User-Friendly Diagnostics: Clang is often praised for its clear, helpful error messages and warnings. This can make it easier to debug and fix code.
  2. Compilation Speed: Clang is often faster at compiling code than GCC.
  3. Modular Design: The LLVM infrastructure is modular, which makes it easier to create and integrate new tools and technologies.
  4. Static Analysis: Clang includes a powerful static analysis tool that can catch many types of bugs and issues at compile time.
  5. Memory Usage: Clang generally uses less memory during compilation than GCC.


  1. Performance: While Clang’s performance is generally very good, there are cases where GCC can produce more efficient code.
  2. Lesser Support for Languages: Clang primarily supports C, C++, and Objective-C. While there is some support for other languages, it’s not as extensive as GCC’s.
  3. GNU Extensions: Clang does not support all of the GNU language extensions that are supported by GCC.

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