Unsurprisingly, one of WebAssembly's primary purposes is to run on the Web, for example embedded in Web browsers (though this is not its only purpose).
This means integrating with the Web ecosystem, leveraging Web APIs, supporting the Web's security model, preserving the Web's portability, and designing in room for evolutionary development. Many of these goals are clearly reflected in WebAssembly's high-level goals. In particular, WebAssembly MVP will be no looser from a security point of view than if the module was JavaScript.
More concretely, the following is a list of points of contact between WebAssembly and the rest of the Web platform that have been considered:
- WebAssembly's modules allow for natural integration with the ES6 module system and allow synchronous calling to and from JavaScript.
- If allowed by the module, JavaScript can alias a loaded module's linear memory via Typed Arrays. (To keep the Typed Arrays' lengths constant, if linear memory is resized, any extant Typed Arrays are detached.)
- WebAssembly's security model should depend on CORS and subresource integrity to enable distribution, especially through content distribution networks and to implement dynamic linking.
- Once threads are supported, a WebAssembly module would
be shared (including its heap) between workers via
postMessage().- This also has the effect of explicitly sharing code so that engines don't perform N fetches and compile N copies.
- WebAssembly may later standardize a more direct way to create a thread that doesn't involve creating a new Worker.
- Once SIMD is supported WebAssembly would:
- Be statically typed analogous to SIMD.js-in-asm.js;
- Reuse specification of operation semantics (with TC39);
- Reuse backend implementation (same IR nodes).
- Once GC is supported, WebAssembly code would be able to reference and access and JS, DOM, and general WebIDL-defined objects.