Book Summary: Clang Compiler Frontend
Hello everyone, I am Amr and i am a Software engineer who is interested in Compiler and Tools development and in this article i will try to write a summary for The Clang Compiler Frontend book so you can get an idea about what is the content and what to expect from it.
The book contains two parts and two Appendices which are.
- Part 1: Clang Setup and Architecture
- Part 2: Clang Tools
- Appendices: Compilation Database and Build Speed Optimization
Part 1: Clang Setup and Architecture
The first part start with config and build Clang project with CMake and Ninja then moving to the architecture of the Clang compiler starting from Lexer, Parser and CodeGen with good level of details on how each part work and how the preprocessor work and why the C++ parser need to depend on Sema (Semantic analysis) and what is a FontEndAction and how to use it.
For me I know from previous talk that the C++ Parser will need to get some information from Sema to parse code successfully but i like that the author provide much deep details and use the LLDB to know what the program doing right now and which component run first.
After that the author go deeper to explain the design of AST (Abstract Syntax Tree) how it structured and how to traverse it in more than one way, for me this chapter was very important for me to optimize traversing the AST in my side project ClangQL because if for example you want to get only class information but you make the visitor recursion on the nodes you will got bad performance because it will traverse fields, methods …etc. and you don’t need them right now.
The last chapter in this part introduce the internal basic libraries and tools for example the LLVM team has his own testing framework that used beside Google test framework (GTest) and also they implemented containers data structures similar to std library but optimized for some common cases such as some String operations, Small Vector …etc
Part 2: Clang tools
The second is moving from the internal architecture of the Clang to the Clang tools starting with how the internal design of the linter which named Clang-tidy and how to config and use it with a practical example on how to create your own custom check that estimate estimate the complexity of a C++ class based on the number of methods it contains and report an error using the Diagnostic engine if the complexity is bigger than a parameter.
Next chapter will introduce advanced code analysis tools based on the Control Flow Graph (CFG) and how to construct CFG and write your own CFG checks.
Next chapter in this part will teach you how to create your own custom code modification tool to do some refactoring such as renaming methods and also how to integrate it with the linter to provide a modification fix for a check, also how to config and use the clang format tool and also how to format your custom modifications.
The last chapter in this part is about the integration with IDE and how the Clangd project provide many useful features such as code complete, go to definition, type hint, linting and code formatting and many other features to your IDE or Code Editor using the Language Server Protocol with many good details so you can imaging what happens under the hood from the file opened until you close the file and how code editor or IDE can communicate with Clangd, also what optimizations tricks the Clangd do to be fast.
Appendix: Compilation Database
In the first appendix the author talk about the compilation database (CDB) what it is and how to use it in a large project and also how it used by other tools such as the Clang-Tidy and Clangd.
Appendix: Build Speed Optimization
This appendix tech you how to use useful features from the Clang to optimize your build speed such as Modulemap, Precompiled headers and modules.
Summary
This book was very useful and exciting to read for me because i am already interested to learn more information about the Clang and LLVM internals and with those information you can work with tools such as linter and formatter with good knowledge how they are works and also implement your own tools, maybe you want to create some checks for your personal or company works or maybe generate a some information from AST or other many ideas for example the ClangQL project extract the AST informations to run SQL query on them.
Also i like how the author use the debugger to show you what exactly happens step by step.
I hope you enjoyed my article, and you can find me on
You can sponsor my work using GitHub Sponsor ❤️ from here.
You can find me on: GitHub, LinkedIn, and Twitter.
Thanks for reading and enjoy Programming 😋.
