arXiv subjects

Yusung Sim

Publications and source records attributed to Yusung Sim.

2 recordsLinked to original sources

arXiv2026

Rust's Type Checker Implementation Is Unsound: An Empirical Study on Soundness Bugs in rustc

Rust is claimed to be a type-sound language capable of preventing various undesirable behaviors, including memory bugs. However, rustc, the official Rust compiler, is not immune to defects; it contains soundness bugs, where the compiler accepts programs that should be rejected during type checking. In this work, we present an empirical study of 30 issues that report potential soundness bugs in rustc, collected from the GitHub issue tracker between January 1, 2022 and September 1, 2025. We analyze each issue in depth, focusing on its affected feature, symptom (how the feature is mishandled), consequence (the resulting undesirable behavior), triggering features, community consensus regarding whether it is a bug, and lifecycle, including introduction, discovery, and fix. Furthermore, we investigate existing artifacts, including implementations such as AddressSanitizer, Miri, Chalk, and a-mir-formality, alongside documentation such as the Rust Reference, the FLS, and Rust RFCs to assess their potential as oracles for testing the type soundness of rustc. Our key findings indicate that: (1) Certain soundness bugs, typically triggered by implied bounds or trait objects, compromise memory safety. (2) Sound type checking is challenged by edge cases involving associated types and the interaction between lifetimes and traits. (3) Most bugs persist from the initial introduction of the relevant features and require significant time to be discovered. (4) While AddressSanitizer and Miri can detect soundness bugs that lead to memory bugs, a-mir-formality and Chalk are currently immature despite their potential to identify other bug categories. (5) Existing documentation frequently fails to provide precise explanations of the language semantics.

cs.SE↗

arXiv2024

Wasm-R3: Record-Reduce-Replay for Realistic and Standalone WebAssembly Benchmarks

WebAssembly (Wasm for short) brings a new, powerful capability to the web as well as Edge, IoT, and embedded systems. Wasm is a portable, compact binary code format with high performance and robust sandboxing properties. As Wasm applications grow in size and importance, the complex performance characteristics of diverse Wasm engines demand robust, representative benchmarks for proper tuning. Stopgap benchmark suites, such as PolyBenchC and libsodium, continue to be used in the literature, though they are known to be unrepresentative. Porting of more complex suites remains difficult because Wasm lacks many system APIs and extracting real-world Wasm benchmarks from the web is difficult due to complex host interactions. To address this challenge, we introduce Wasm-R3, the first record and replay technique for Wasm. Wasm-R3 transparently injects instrumentation into Wasm modules to record an execution trace from inside the module, then reduces the execution trace via several optimizations, and finally produces a replay module that is executable sandalone without any host environment - on any engine. The benchmarks created by our approach are (i) realistic, because the approach records real-world web applications, (ii) faithful to the original execution, because the replay benchmark includes the unmodified original code, only adding emulation of host interactions, and (iii) standalone, because the replay benchmarks run on any engine. Applying Wasm-R3 to web-based Wasm applications in the wild demonstrates the correctness of our approach as well as the effectiveness of our optimizations, which reduce the recorded traces by 99.53 percent and the size of the replay benchmark by 9.98 percent. We release the resulting benchmark suite of 27 applications, called Wasm-R3-Bench, to the community, to inspire a new generation of realistic and standalone Wasm benchmarks.

cs.PL↗