Choosing the Right Interface for Your Application¶
Clang provides infrastructure to write tools that need syntactic and semantic information about a program. This document will give a short introduction of the different ways to write clang tools, and their pros and cons.
LibClang¶
LibClang is a stable high level C interface to clang. When in doubt LibClang is probably the interface you want to use. Consider the other interfaces only when you have a good reason not to use LibClang.
Canonical examples of when to use LibClang:
- Xcode 
- Clang Python Bindings 
Use LibClang when you...:
- want to interface with clang from other languages than C++ 
- need a stable interface that takes care to be backwards compatible 
- want powerful high-level abstractions, like iterating through an AST with a cursor, and don't want to learn all the nitty gritty details of Clang's AST. 
Do not use LibClang when you...:
- want full control over the Clang AST 
Clang Plugins¶
Clang Plugins allow you to run additional actions on the AST as part of a compilation. Plugins are dynamic libraries that are loaded at runtime by the compiler, and they're easy to integrate into your build environment.
Canonical examples of when to use Clang Plugins:
- special lint-style warnings or errors for your project 
- creating additional build artifacts from a single compile step 
Use Clang Plugins when you...:
- need your tool to rerun if any of the dependencies change 
- want your tool to make or break a build 
- need full control over the Clang AST 
Do not use Clang Plugins when you...:
- want to run tools outside of your build environment 
- want full control on how Clang is set up, including mapping of in-memory virtual files 
- need to run over a specific subset of files in your project which is not necessarily related to any changes which would trigger rebuilds 
LibTooling¶
LibTooling is a C++ interface aimed at writing standalone tools, as well as integrating into services that run clang tools. Canonical examples of when to use LibTooling:
- a simple syntax checker 
- refactoring tools 
Use LibTooling when you...:
- want to run tools over a single file, or a specific subset of files, independently of the build system 
- want full control over the Clang AST 
- want to share code with Clang Plugins 
Do not use LibTooling when you...:
- want to run as part of the build triggered by dependency changes 
- want a stable interface so you don't need to change your code when the AST API changes 
- want high level abstractions like cursors and code completion out of the box 
- do not want to write your tools in C++ 
Clang tools are a collection of specific developer tools built on top of the LibTooling infrastructure as part of the Clang project. They are targeted at automating and improving core development activities of C/C++ developers.
Examples of tools we are building or planning as part of the Clang project:
- Syntax checking (clang-check) 
- Automatic fixing of compile errors (clang-fixit) 
- Automatic code formatting (clang-format) 
- Migration tools for new features in new language standards 
- Core refactoring tools