Stories with Tag C

• An effect system proposal for C2y

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  Posted: 2025-01-18 19:00:26

  Verbose tl;dr

  This proposal introduces an effect system to C2x, aiming to enhance code modularity, optimization, and correctness by explicitly declaring and checking the side effects of functions. It defines a set of effect keywords, like reads and writes, to annotate function parameters and return values, indicating how they are accessed. These annotations are part of the function's type and are checked by the compiler, ensuring that declared effects match the function's actual behavior. The proposal also includes a mechanism for polymorphism over effects, enabling more flexible code reuse and separate compilation without sacrificing effect safety. This mechanism allows for abstracting over effects, so that functions can be written generically to operate on data structures with varying levels of mutability.

  This document, titled "An Effect System Proposal for C2y," proposes an extension to the C2y programming language (a hypothetical successor to C2x, itself a successor to C17/C11, aiming to modernize C) by introducing an effect system. This system aims to provide a more structured and reliable way to manage side effects within C programs, enhancing code clarity, maintainability, and potentially enabling compiler optimizations.

  The core of the proposal revolves around explicitly declaring the potential side effects of functions using effect specifications. These specifications, integrated into function declarations, enumerate the possible side effects a function might have. Examples of such effects include allocating memory, accessing files, throwing exceptions, and modifying global state. A distinct "pure" effect specification designates functions with no observable side effects beyond their return value.

  The effect system operates based on a set of pre-defined effect keywords, allowing for granular control over side effect categorization. For instance, separate effects might differentiate between reading and writing to files, enabling finer-grained analysis. The proposal introduces new syntax for declaring these effects within function signatures, using a dedicated keyword (like effects) followed by a parenthesized, comma-separated list of effect specifiers.

  The proposal outlines how effect specifications interact with function calls. A function's declared effects must encompass all possible side effects that could occur during its execution, including those of any functions it calls. The compiler verifies these effect specifications, ensuring that no undeclared side effects are present. This static checking prevents accidental or undocumented side effects, leading to more robust and predictable code.

  Beyond basic effect declarations, the proposal delves into more advanced features, such as effect polymorphism. This mechanism allows functions to operate on data with different effect specifications, promoting code reuse without compromising the strictness of the effect system. It introduces the concept of effect variables within function declarations, which act as placeholders for specific effects that are determined at the call site.

  The document further explores the implications of effect systems for existing C features. It addresses how effects interact with function pointers, suggesting the inclusion of effect specifications within function pointer types. It also discusses the handling of effects within variadic functions and macros, recognizing the challenges these present and outlining potential solutions.

  Finally, the proposal considers the interaction between effects and exception handling. It proposes a connection between thrown exceptions and the effect system, allowing exceptions to be declared as potential side effects and enabling more comprehensive error management within the framework of the effect system. This integration ensures that exceptions are treated as part of the overall side effect analysis, further contributing to the reliability and predictability of the code. The document concludes by suggesting areas for future research and development, such as integration with concurrency features and the exploration of more sophisticated effect analysis techniques.

  • C
  • C2y
  • C2x
  • programming language
  • effect systems
  • type systems
  • static analysis
  • language design
  • proposal
  • WG14
  • ISO
  • standardization
  • Functional Programming
  • side effects
  • algebraic effects

  Summary of Comments ( 6 )
  https://news.ycombinator.com/item?id=42750517

  Verbose tl;dr

  The Hacker News comments on the C2y effect system proposal express a mix of skepticism and cautious interest. Several commenters question the practicality and performance implications of implementing such a system in C, citing the language's existing complexity and the potential for significant overhead. Concerns are raised about the learning curve for developers and the possibility of introducing subtle bugs. Some find the proposal intriguing from a research perspective but doubt its widespread adoption. A few express interest in exploring the potential benefits of improved code analysis and error detection, particularly for concurrency and memory management, though acknowledge the challenges involved. Overall, the consensus leans towards viewing the proposal as an interesting academic exercise with limited real-world applicability in its current form.

  The Hacker News post "An effect system proposal for C2y" links to a 2023 draft of N3317, a proposal for adding an effect system to a future version of the C programming language (then tentatively called C2y, now C2x). The discussion on Hacker News is relatively brief, consisting of only a few comments, and doesn't delve very deep into the technical details of the proposal.

  One commenter expresses skepticism about the proposal's practicality, wondering whether the added complexity of an effect system would outweigh its benefits for typical C programming tasks. They question whether the kind of guaranteed safety that effect systems provide is truly necessary or desirable in the C ecosystem, where performance and low-level control are often prioritized. This commenter explicitly states they would not want to use an effects system in C, even if it were fully baked and easy to use. They view effects systems as more suited to functional languages, and fundamentally at odds with the design ethos and intended use cases of C.

  Another commenter focuses on the evolution of C standards, noting the long period between revisions and the challenges in introducing significant changes to a language with such a large and established codebase. They also point out that alternative languages or extensions already offer some form of effect systems or related features, implying that developers needing such features might prefer those options rather than waiting for a potentially complex and slow-to-be-adopted change in the C standard itself. They mention Zig as a modern C-like language and Rust as two examples with stricter, more sophisticated type and safety features.

  Finally, one commenter briefly remarks on the proposal's age (dating back to 2023), suggesting that its status and likelihood of incorporation into a future C standard are uncertain. This comment highlights the long process of standardization and the possibility that the proposal might be superseded by other developments in the meantime.

• Compiling C to Safe Rust, Formalized

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  Posted: 2024-12-20 23:30:03

  Verbose tl;dr

  This paper introduces Crusade, a formally verified translation from a subset of C to safe Rust. Crusade targets a memory-safe dialect of C, excluding features like arbitrary pointer arithmetic and casts. It leverages the Coq proof assistant to formally verify the translation's correctness, ensuring that the generated Rust code behaves identically to the original C, modulo non-determinism inherent in C. This rigorous approach aims to facilitate safe integration of legacy C code into Rust projects without sacrificing confidence in memory safety, a critical aspect of modern systems programming. The translation handles a substantial subset of C, including structs, unions, and functions, and demonstrates its practical applicability by successfully converting real-world C libraries.

  The arXiv preprint "Compiling C to Safe Rust, Formalized" details a novel approach to automatically translating C code into memory-safe Rust code. This process aims to leverage the performance benefits of C while inheriting the robust memory safety guarantees offered by Rust, thereby mitigating the pervasive vulnerability landscape associated with C programming.

  The authors introduce a sophisticated compilation pipeline founded on a formal semantic model. This model rigorously defines the behavior of both the source C code and the target Rust code, enabling a precise and verifiable translation process. The core of this pipeline utilizes a "stacked borrows" model, a memory management strategy adopted by Rust that enforces strict rules regarding shared mutable references and mutable borrows to prevent data races and memory corruption. The translation procedure systematically transforms C pointers into Rust references governed by these stacked borrows rules, ensuring that the resulting Rust code adheres to the same memory safety principles inherent in Rust's design.

  A key challenge addressed by the paper is the handling of C's flexible pointer arithmetic and unrestricted memory access patterns. The authors introduce a concept of "ghost state" within the formal model. This ghost state tracks the provenance and validity of pointers throughout the C code, allowing the compiler to reason about pointer relationships and enforce memory safety during translation. This information is then leveraged to generate corresponding safe Rust constructs, such as safe references and bounds checks, that mirror the intended behavior of the original C code while respecting Rust's stricter memory model.

  The paper demonstrates the effectiveness of their approach through a formalization within the Coq proof assistant. This formalization rigorously verifies the soundness of the translation process, proving that the generated Rust code preserves the semantics of the original C code while guaranteeing memory safety. This rigorous verification provides strong evidence for the correctness and reliability of the proposed compilation technique.

  Furthermore, the authors outline how their approach accommodates various C language features, including function pointers, structures, and unions. They describe how these features are mapped to corresponding safe Rust equivalents, thereby expanding the scope of the translation process to cover a wider range of C code.

  While the paper primarily focuses on the formal foundations and theoretical aspects of the C-to-Rust translation, it also lays the groundwork for future development of a practical compiler toolchain based on these principles. Such a toolchain could offer a valuable pathway for migrating existing C codebases to a safer environment while minimizing manual rewriting effort and preserving performance characteristics. The formal verification aspect provides a high degree of confidence in the safety of the translated code, a crucial consideration for security-critical applications.

  • C
  • Rust
  • Compilers
  • Formal Verification
  • Safety
  • Programming Languages
  • Code Translation
  • Transpilation
  • Automated Reasoning
  • formal methods
  • software engineering
  • Software Security
  • static analysis
  • Memory Safety
  • Type Safety
  • Correctness
  • Semantics
  • Crux
  • CakeML

  Summary of Comments ( 157 )
  https://news.ycombinator.com/item?id=42476192

  Verbose tl;dr

  HN commenters discuss the challenges and nuances of formally verifying the C to Rust transpiler, Cracked. Some express skepticism about the practicality of fully verifying such a complex tool, citing the potential for errors in the formal proofs themselves and the inherent difficulty of capturing all undefined C behavior. Others question the performance impact of the generated Rust code. However, many commend the project's ambition and see it as a significant step towards safer systems programming. The discussion also touches upon the trade-offs between a fully verified transpiler and a more pragmatic approach focusing on common C patterns, with some suggesting that prioritizing practical safety improvements could be more beneficial in the short term. There's also interest in the project's handling of concurrency and the potential for integrating Cracked with existing Rust tooling.

  The Hacker News post titled "Compiling C to Safe Rust, Formalized" (https://news.ycombinator.com/item?id=42476192) has generated a moderate amount of discussion, with several commenters exploring different aspects of the C to Rust transpilation process and its implications.

  One of the most prominent threads revolves around the practical benefits and challenges of such a conversion. A commenter points out the potential for improved safety and maintainability by leveraging Rust's ownership and borrowing system, but also acknowledges the difficulty in translating C's undefined behavior into a Rust equivalent. This leads to a discussion about the trade-offs between preserving the original C code's semantics and enforcing Rust's stricter safety guarantees. The difficulty of handling C's reliance on pointer arithmetic and manual memory management is highlighted as a major hurdle.

  Another key area of discussion centers around the performance implications of the transpilation. Commenters speculate about the potential for performance improvements due to Rust's closer-to-the-metal nature and its ability to optimize memory access. However, others raise concerns about the overhead introduced by Rust's safety checks and the potential for performance regressions if the translation isn't carefully optimized. The question of whether the generated Rust code would be idiomatic and performant is also raised.

  The topic of formal verification and its role in ensuring the correctness of the translation is also touched upon. Commenters express interest in the formalization aspect, recognizing its potential to guarantee that the translated Rust code behaves equivalently to the original C code. However, some skepticism is voiced about the practicality of formally verifying complex C codebases and the potential for subtle bugs to slip through even with formal methods.

  Finally, several commenters discuss alternative approaches to improving the safety and security of C code, such as using static analysis tools or employing safer subsets of C. The transpilation approach is compared to these alternatives, with varying opinions on its merits and drawbacks. The overall sentiment seems to be one of cautious optimism, with many acknowledging the potential of C to Rust transpilation but also recognizing the significant challenges involved.

• Hobby Project: A dynamic C (Hot reloading) module-based Web Framework

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  Posted: 2024-11-17 18:12:14

  Verbose tl;dr

  This project introduces a C-based web framework designed for dynamic module loading and hot reloading. Leveraging a custom module format and a simple HTTP server, it allows developers to modify and reload C code without restarting the server, facilitating rapid development and experimentation. The framework compiles and links modules on-the-fly, managing dependencies and updating the running server seamlessly. While currently limited in features, it aims to offer a performant and flexible foundation for building web applications directly in C.

  This GitHub project, titled "Hobby Project: A dynamic C (Hot reloading) module-based Web Framework," details the development of a web framework written entirely in C, with a focus on dynamic module loading and hot reloading capabilities. The author's primary goal is to create a system where modifying and recompiling individual modules doesn't necessitate restarting the entire web server, thereby significantly streamlining the development workflow. This is achieved through a modular architecture where functionality is broken down into separate, dynamically linked libraries (.so files on Linux/macOS, .dll files on Windows).

  The framework utilizes a central core responsible for handling incoming HTTP requests and routing them to the appropriate modules. These modules, compiled as shared libraries, can be loaded, unloaded, and reloaded at runtime without interrupting the server's operation. This dynamic loading is facilitated through the use of dlopen and related functions (or their Windows equivalents). When a module is modified and recompiled, the framework detects the change and automatically reloads the updated library, making the new code immediately active.

  The project utilizes a custom configuration file, likely in a format like JSON or INI, to define routes and associate them with specific modules and their respective functions. This allows for flexible mapping of URLs to specific functionalities provided by the loaded modules.

  The hot reloading mechanism likely involves some form of file system monitoring to detect changes in module files. Upon detection of a change, the framework gracefully unloads the old module, loads the newly compiled version, and updates the routing table accordingly. This process minimizes downtime and allows for continuous development and testing without restarting the server.

  While the project is explicitly labelled as a hobby project, suggesting it isn't intended for production use, it explores an interesting approach to web framework design in C. The focus on modularity and dynamic reloading offers potential advantages in terms of development speed and flexibility. The implementation details provided in the repository offer insights into the challenges and considerations involved in building such a system in C, including memory management, inter-module communication, and handling potential errors during dynamic loading and unloading.

  • C
  • Web Framework
  • Dynamic Modules
  • Hot Reloading
  • Hobby Project
  • Module-based
  • C Programming
  • Web Development
  • Open Source
  • GitHub
  • Software Development
  • Dynamic Linking
  • Code Reloading
  • programming
  • Shared Libraries
  • Modular Design
  • System Programming

  Summary of Comments ( 50 )
  https://news.ycombinator.com/item?id=42165759

  Verbose tl;dr

  Hacker News users discussed the practicality and novelty of a C web framework with hot reloading. Some questioned the real-world use cases and performance benefits compared to existing solutions, suggesting the project serves more as an interesting experiment than a production-ready tool. Others expressed interest in the technical implementation, particularly the hot reloading aspect, and appreciated the author's effort in exploring this concept. Several users pointed out potential issues like memory leaks and the challenges of safely reloading C code in a web server environment. The overall sentiment leans towards acknowledging the project's technical ingenuity while remaining skeptical about its broad applicability.

  The Hacker News post "Hobby Project: A dynamic C (Hot reloading) module-based Web Framework" linking to the GitHub project c-web-modules sparked a moderate discussion with a mix of curiosity, skepticism, and praise.

  Several commenters expressed intrigue about the project's hot reloading capabilities in C, wondering about the implementation details and its effectiveness. One user questioned how the hot reloading handles global state and potential memory leaks, a crucial aspect of dynamic module loading. Another user highlighted the project's apparent focus on simplicity, which they found appealing. This comment received further engagement, with another user agreeing about the simplicity while also noting the potential limitations due to its single-threaded nature.

  The project's use of inotify for monitoring file changes and triggering recompilation/reloading was also discussed, with some expressing concern about its performance implications, especially under heavy load or with a large number of modules.

  A few commenters drew parallels with other projects and technologies. One mentioned how this approach reminded them of Erlang's hot code swapping, highlighting the benefit of minimizing downtime during development. Another commenter discussed similar hot reloading mechanisms found in other web frameworks like Django, though acknowledging the differences in language and complexity.

  Some skepticism was directed towards the practicality and potential use cases of such a framework. One commenter questioned the target audience and whether there was a significant need for a dynamic C web framework, given the prevalence of more established options.

  Despite some doubts, the overall sentiment towards the project was positive, with many appreciating it as an interesting experiment and a demonstration of what's possible with C. The project author also engaged in the comments, responding to questions and providing further insights into the project's goals and design choices. They clarified that the primary motivation was personal exploration and learning rather than building a production-ready framework, emphasizing its hobbyist nature. This transparency was generally well-received by the community.