429334cf98
We at one point considered making `ModuleBuilder` create complete WebAssembly binaries. However, we recently spun out [wabin](https://github.com/tetratelabs/wabin), which allows this. Meanwhile, the features in `ModuleBuilder` were confusing and misused. For example, the only two cases memory was exported on GitHub were done by accident. This is because host functions act on the guest's memory, not their own. Hence, this removes memory and globals from host side definitions, and renames the type to HostModuleBuilder to clarify this is not ever going to be used to construct normal Wasm binaries. Most importantly, this simplifies the API and reduces a lot of code. It is important to make changes like this, particularly deleting any experimental things that didn't end up useful. Signed-off-by: Adrian Cole <adrian@tetrate.io> Co-authored-by: Anuraag Agrawal <anuraaga@gmail.com>
Rust allocation example
This example shows how to pass strings in and out of a Wasm function defined
in Rust, built with cargo build --release --target wasm32-unknown-unknown
Ex.
$ go run greet.go wazero
Hello, wazero!
Under the covers, lib.rs does a few things of interest:
- Uses a WebAssembly-tuned memory allocator: wee_alloc.
- Exports wrapper functions to allocate and deallocate memory.
- Uses
&strinstead of CString (NUL-terminated strings). - Uses
std::mem::forgetto prevent Rust from eagerly freeing pointers returned.
Note: We chose to not use CString because it keeps the example similar to how you would track memory for arbitrary blobs. We also watched function signatures carefully as Rust compiles different WebAssembly signatures depending on the input type.
See https://wazero.io/languages/rust/ for more tips.