While wasm32-wasi and wasm32-unknown-emscripten include an interface for system functions to be provided by the host, wasm32-unknown-unknown is limited by communicationg with primitive types only.
In this example, we use a subset of OpenBSD libc and link it statically to store a value in the heap from C with malloc() and free().
On top of the existing functions from the previous examples, this crate implements a simple Memory feature in the calculator, which can store and retrieve a number by using store(), retrieve(), and clear() functions defined in C.
As an alternative to renaming the C symbols like we did in the last example, this crate adds a common prefix to the exported symbols instead:
calculator_add()calculator_subtract()calculator_multiply()calculator_divide()calculator_store()calculator_retrieve()calculator_clear()
Only subtract() and multiply() are defined in Rust.
One could write a JS wrapper manually to convert these functions to a more idiomatic JavaScript class. However, the recommended way of doing that is by using wasm-bindgen, which is demonstrated in the next example.
The original wasm32-unknown-unknown-openbsd-libc was created by @trevyn.