[OCaML'23] MetaOCaml Theory and Implementation Oleg Kiselyov Quasi-quotation (or, code templates) has long been used as a convenient tool for code generation, commonly implemented as a pre-processing/translation into code-generation combinators. The original MetaOCaml was also based on such translation, done post type checking. BER MetaOCaml employs a significantly different, efficient (especially in version N114) translation integrated with type-checking, in the least intrusive way. This paper presents the integrated efficient translation for the first time.

[OCaML'23] Owi: an interpreter and a toolkit for WebAssembly written in OCaml Léo Andrès, Pierre Chambart, Eric Patrizio, Dario Pinto This presentation introduces Owi, an OCaml-based interpreter and toolkit for WebAssembly (Wasm). Owi aims to provide a fast and easily maintainable solution for Wasm code execution. Unlike competing interpreters, Owi focuses on facilitating experimentation, research, and symbolic manipulations of Wasm. We describe the different passes and intermediate representations of Owi. Additionally, we discuss the linker, the interpreter and its support for various Wasm-specific extensions. Owi’s API leverages Generalized Algebraic Data Types (GADTs) for improved error detection at link-time. We also describe the testing methods used, including a Crowbar-based fuzzer. Future work includes incorporating missing Wasm extensions, implementing advanced optimization passes, and potentially porting the WASP execution engine to perform concolic execution.

[OCaML'23] Owi: an interpreter and a toolkit for WebAssembly written in OCaml Léo Andrès, Pierre Chambart, Eric Patrizio, Dario Pinto This presentation introduces Owi, an OCaml-based interpreter and toolkit for WebAssembly (Wasm). Owi aims to provide a fast and easily maintainable solution for Wasm code execution. Unlike competing interpreters, Owi focuses on facilitating experimentation, research, and symbolic manipulations of Wasm. We describe the different passes and intermediate representations of Owi. Additionally, we discuss the linker, the interpreter and its support for various Wasm-specific extensions. Owi’s API leverages Generalized Algebraic Data Types (GADTs) for improved error detection at link-time. We also describe the testing methods used, including a Crowbar-based fuzzer. Future work includes incorporating missing Wasm extensions, implementing advanced optimization passes, and potentially porting the WASP execution engine to perform concolic execution.

[OCaML'23] Building a lock-free STM for OCaml Vesa Karvonen, Bartosz Modelski, Carine Morel, Thomas Leonard, KC Sivaramakrishnan, YSS Narasimha Naidu, Sudha Parimala The kcas library was originally developed to provide a primitive atomic lock-free multi-word compare-and-set operation. This talk introduces kcas and discusses the recent development of kcas turning it into a proper lock-free software transactional memory implementation for OCaml that provides composable transactions, scheduler friendly modular blocking, and comes with a companion library of composable lock-free data structures.

[OCaML'23] Building a lock-free STM for OCaml Vesa Karvonen, Bartosz Modelski, Carine Morel, Thomas Leonard, KC Sivaramakrishnan, YSS Narasimha Naidu, Sudha Parimala The kcas library was originally developed to provide a primitive atomic lock-free multi-word compare-and-set operation. This talk introduces kcas and discusses the recent development of kcas turning it into a proper lock-free software transactional memory implementation for OCaml that provides composable transactions, scheduler friendly modular blocking, and comes with a companion library of composable lock-free data structures.

[OCaML'23] Targeted Static Analysis for OCaml C Stubs: Eliminating gremlins from the code Edwin Török Migration to OCaml 5 requires updating a lot of C bindings due to the removal of naked pointer support. Writing OCaml user-defined primitives in C is a necessity, but is unsafe and error-prone. It does not benefit from either OCaml’s or C’s type checking, and existing C static analysers are not aware of the OCaml GC safety rules, and cannot infer them from existing macros alone. The alternative is automatically generating C stubs, which requires correctly managing value lifetimes. Having a static analyser for OCaml to C interfaces is useful outside the OCaml 5 porting effort too. After some motivating examples of real bugs in C bindings a static analyser is presented that finds these known classes of bugs. The tool works on the OCaml abstract parse and typed trees, and generates a header file and a caller model. Together with a simplified model of the OCaml runtime this is used as input to a static analysis framework, Goblint. An analysis is developed that tracks dereferences of OCaml values, and together with the existing framework reports incorrect dereferences. An example is shown how to extend the analysis to cover more safety properties. The tools and runtime models are generic and could be reused with other static analysis tools.

[OCaML'23] Targeted Static Analysis for OCaml C Stubs: Eliminating gremlins from the code Edwin Török Migration to OCaml 5 requires updating a lot of C bindings due to the removal of naked pointer support. Writing OCaml user-defined primitives in C is a necessity, but is unsafe and error-prone. It does not benefit from either OCaml’s or C’s type checking, and existing C static analysers are not aware of the OCaml GC safety rules, and cannot infer them from existing macros alone. The alternative is automatically generating C stubs, which requires correctly managing value lifetimes. Having a static analyser for OCaml to C interfaces is useful outside the OCaml 5 porting effort too. After some motivating examples of real bugs in C bindings a static analyser is presented that finds these known classes of bugs. The tool works on the OCaml abstract parse and typed trees, and generates a header file and a caller model. Together with a simplified model of the OCaml runtime this is used as input to a static analysis framework, Goblint. An analysis is developed that tracks dereferences of OCaml values, and together with the existing framework reports incorrect dereferences. An example is shown how to extend the analysis to cover more safety properties. The tools and runtime models are generic and could be reused with other static analysis tools.

[OCaML'23] Less Power for More Learning: Restricting OCaml Features for Effective Teaching Max Lang, Nico Petzendorfer We present a framework for sandboxing and restricting features of the OCaml programming language to effectively automate the grading of programming exercises, scaling to hundreds of submissions. We describe how to disable language and library features that should not be used to solve a given exercise. We present an overview of an implementation of a mock IO system to allow testing of IO-related exercises in a controlled environment. Finally, we detail a number of security considerations to ensure submitted code remains sandboxed, allowing automatic grading to be trusted without manual verification. The source code of our implementation is publicly available [1]. [1] As a git repository at https://github.com/just-max/less-power.

[OCaML'23] Less Power for More Learning: Restricting OCaml Features for Effective Teaching Max Lang, Nico Petzendorfer We present a framework for sandboxing and restricting features of the OCaml programming language to effectively automate the grading of programming exercises, scaling to hundreds of submissions. We describe how to disable language and library features that should not be used to solve a given exercise. We present an overview of an implementation of a mock IO system to allow testing of IO-related exercises in a controlled environment. Finally, we detail a number of security considerations to ensure submitted code remains sandboxed, allowing automatic grading to be trusted without manual verification. The source code of our implementation is publicly available [1]. [1] As a git repository at https://github.com/just-max/less-power.

[OCaML'23] Parallel Sequences in Multicore OCaml Andrew Tao I present my implementation of a parallel sequences abstraction that utilizes the support for shared memory parallelism in the new OCaml 5.0.0 multicore runtime. This abstraction allows clients to create highly parallelizable programs without needing to write, or even understand, the low-level implementation details necessary to parallelize large tasks.