Why Chrome Enabled WebAssembly Garbage Collection (WasmGC) By Default

In Chrome, JavaScript (and WebAssembly) code are both executed by Google's open source V8 engine - which already has garbage-collecting capabilities. "This means developers making use of, for example, PHP compiled to Wasm, end up shipping a garbage collector implementation of the ported language (PHP) to the browser that already has a garbage collector," writes Google developer advocate Thomas Steiner, "which is as wasteful as it sounds." "This is where WasmGC comes in."WebAssembly Garbage Collection (or WasmGC) is a proposal of the WebAssembly Community Group [which] adds struct and array heap types, which means support for non-linear memory allocation... In simplified terms, this means that with WasmGC, porting a programming language to WebAssembly means the programming language's garbage collector no longer needs to be part of the port, but instead the existing garbage collector can be used. Sometime on Halloween, Steiner wrote that in Chrome, WebAssembly garbage collection is now enabled by default. But then he explored what this means for high-level programming languages (with their own built-in garbage collection) being compiled into WebAssembly:To verify the real-world impact of this improvement, Chrome's Wasm team has compiled versions of the Fannkuch benchmark (which allocates data structures as it works) from C, Rust, and Java. The C and Rust binaries could be anywhere from 6.1 K to 9.6 K depending on the various compiler flags, while the Java version is much smaller at only 2.3 K! C and Rust do not include a garbage collector, but they do still bundle malloc/free to manage memory, and the reason Java is smaller here is because it doesn't need to bundle any memory management code at all. This is just one specific example, but it shows that WasmGC binaries have the potential of being very small, and this is even before any significant work on optimizing for size. The blog post includes two examples of WasmGC-ported programming languages in action:"One of the first programming languages that has been ported to Wasm thanks to WasmGC is Kotlin in the form of Kotlin/Wasm.""The Dart and Flutter teams at Google are also preparing support for WasmGC. The Dart-to-Wasm compilation work is almost complete, and the team is working on tooling support for delivering Flutter web applications compiled to WebAssembly."

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