This blog post chronicles the author's weekend project of building a compiler for a simplified C-like language. It walks through the implementation of a lexical analyzer, parser (using recursive descent), and code generator targeting x86-64 assembly. The compiler handles basic arithmetic operations, variable declarations and assignments, if/else statements, and while loops. The post emphasizes simplicity and educational value over performance or completeness, providing a practical example of compiler construction principles in a digestible format. The code is available on GitHub for readers to explore and experiment with.
This blog post, "TinyCompiler: A compiler in a week-end," chronicles the author's journey in creating a simplified compiler from scratch over a weekend. The primary goal wasn't to build a production-ready tool but rather a practical learning exercise to solidify the author's understanding of compiler construction principles. The compiler targets Monkey, a language inspired by the author's previous Monkey interpreter project. The post meticulously details each stage of the compiler's development, emphasizing clarity and simplicity over optimization or feature completeness.
The process begins with lexical analysis (lexing), which transforms the raw Monkey source code into a stream of tokens. These tokens represent meaningful units like keywords, identifiers, operators, and punctuation. The author employs regular expressions to recognize these patterns in the input string and generate corresponding token objects. The post includes snippets of C++ code demonstrating the implementation of this lexing process.
Following lexing, the compiler proceeds to parsing. The parser takes the stream of tokens and organizes them into an Abstract Syntax Tree (AST). This tree-like structure represents the grammatical structure of the source code, making it easier to analyze and manipulate. The author uses a recursive descent parsing technique, writing functions to handle each grammatical rule of the Monkey language. The post explains how the parser combines tokens into higher-level constructs like expressions, statements, and program blocks, mirroring the grammar rules defined for Monkey. Code examples illustrating the recursive nature of the parsing process are provided.
The final stage covered in the post is code generation. With the AST constructed, the compiler translates it into assembly language for a hypothetical stack-based virtual machine. This process involves traversing the AST and emitting corresponding assembly instructions for each node. The post demonstrates how different AST nodes, representing various language constructs, are converted into equivalent VM instructions. The chosen assembly language targets a simple virtual machine, enabling the author to focus on the core principles of code generation without delving into the complexities of a real-world target architecture. The post includes detailed explanations and C++ code snippets showing how arithmetic expressions, variable assignments, and conditional statements are translated into assembly instructions. The author acknowledges that this simple compiler lacks optimization and error handling features, prioritizing educational value over practical utility. The post concludes by reflecting on the learning experience and offering potential avenues for extending the project further.
Summary of Comments ( 58 )
https://news.ycombinator.com/item?id=43120873
HN users largely praised the TinyCompiler project for its educational value, highlighting its clear code and approachable structure as beneficial for learning compiler construction. Several commenters discussed extending the compiler's functionality, such as adding support for different architectures or optimizing the generated code. Some pointed out similar projects or resources, like the "Let's Build a Compiler" tutorial and the Crafting Interpreters book. A few users questioned the "weekend" claim in the title, believing the project would take significantly longer for a novice to complete. The post also sparked discussion about the practical applications of such a compiler, with some suggesting its use for educational purposes or embedding in resource-constrained environments. Finally, there was some debate about the complexity of the compiler compared to more sophisticated tools like LLVM.
The Hacker News post "TinyCompiler: A compiler in a week-end" generated a fair amount of discussion, with several commenters sharing their perspectives and experiences related to compiler construction.
A prevalent theme in the comments is the accessibility and educational value of the project. Many commenters praised the author for creating a simplified yet functional compiler, making the often-daunting task of compiler development more approachable for beginners. Some users shared their personal experiences of using similar projects as a starting point for learning about compilers, emphasizing the importance of hands-on projects in grasping the underlying concepts.
Several comments delve into technical details, discussing specific aspects of the compiler's implementation, such as the parsing techniques, code generation strategies, and the choice of target language (assembly). Some commenters pointed out potential improvements or alternative approaches, fostering a constructive discussion about compiler design choices. For example, there's discussion around the use of recursive descent parsing and the handling of operator precedence.
A few comments touch upon the project's scope and limitations. While acknowledging the project's educational merit, some commenters rightly point out that it's a simplified example and doesn't cover the full complexity of real-world compilers. They mention aspects like optimization, error handling, and support for more advanced language features as areas where the tiny compiler differs from production-ready compilers.
The value of such simplified projects as learning tools is a recurring point of discussion. Commenters argue that focusing on a smaller, manageable project allows beginners to grasp the fundamental principles without being overwhelmed by the intricacies of a full-blown compiler. This sentiment reinforces the project's goal of making compiler development accessible to a wider audience.
Finally, some comments offer links to related resources, including other compiler tutorials, open-source compiler projects, and books on compiler construction. This further contributes to the educational value of the discussion, providing avenues for those interested in exploring the topic further.