Tail Calls for Language Semantics and Engine Internals

Andreas Rossberg unpacks WASM 3.0, covering new capabilities like garbage collection, exception handling, tail calls, and support for 64-bit addressing with multiple memories. The discussion explores deterministic profiles following relaxed sim, WebAssembly’s capability-based security model, and advances in sandboxing and module design. Andreas connects these features to practical use cases in JavaScript engines and applications like Google Sheets, then looks ahead to experimental work on threading, stack switching, and async programming models shaping the next phase of the WebAssembly ecosystem.

Links

Website: https://people.mpi-sws.org/~rossberg
GitHub: https://github.com/rossberg

Resources

WASM 3.0 Completed: https://webassembly.org/news/2025-09-17-wasm-3.0

Chapters

00:00 Intro – Andreas Rossberg and the WebAssembly 3.0 Update
01:05 The State of WebAssembly Today
02:15 Why WebAssembly Exists Beyond the Web
03:20 From WebAssembly 2.0 to 3.0 – What’s Actually New
04:30 Garbage Collection: A Game-Changer for Managed Languages
06:00 The Vision of WebAssembly as a Universal Compilation Target
07:40 How GC Support Unlocks Java, Kotlin, and Dart on WASM
09:10 Expanding to 64-bit Memory – Performance and Limits
10:40 WebAssembly for Databases, AI, and LLMs
12:00 Sandboxing and Security by Design
13:10 How Capabilities and Static Analysis Keep WASM Safe
14:30 Multi-Memory Support and Real-World Use Cases
16:00 Developer Ergonomics vs. Specification Purity
17:20 Tail Calls and Functional Programming Benefits
18:40 Function Tables and Secure Indirection
20:00 Exception Handling Finally Arrives
21:10 Determinism, Efficiency, and Why It Matters for Blockchain
22:30 SIMD and Hardware Divergence Across Platforms
24:00 Balancing Portability with Performance
25:20 The Design Philosophy Behind WebAssembly
26:30 Why WASM Rejects Language-Specific Features
27:40 Proposal Process: Who Decides What Gets In
29:00 Browser Vendors and Implementation Challenges
30:10 Early Deployments: GC, Tooling, and Adoption Stories
31:30 Threads, Stack Switching, and the Future of Concurrency
33:00 Async/Await and Coroutines on WebAssembly
34:30 What’s Coming Next for WASM Developers
35:40 How to Get Involved – Working Groups and Proposals
37:00 Closing Thoughts and Thanks

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