What's the specific benefit for trying to make the switch for WASI when "there's no support for the instructions in the clang C front end, nor really in the backend yet" as I don't think wasmtime has landed their GC proposal support fully yet? Plus there isn't a WASI trampoline like there is with Emscripten, so I'm not sure where you're suggesting to insert the assembly code, unless you're trying to broaden the trampoline to be WASM-agnostic?

Right well if wasmtime or your favorite wasi runtime don't support wasm-gc yet then there's no benefit until they do. But wasi has the same function pointer cast problem as emscripten. Once the wasi runtimes all support wasm I think it makes sense to think about how to get a trampoline running. But it is indeed annoying if it's necessary to hand craft an object file. I'll look into what the options are, maybe there's a reasonable way with a .s file or inline assembly.

if wasmtime or your favorite wasi runtime don't support wasm-gc yet then there's no benefit until they do.

Looks like I misspoke; wasmtime landed support in version 27 in late November.