Reduce wasm file size by not static link libs like swiftCore

[didi11641]

I have compiled a 'hello world' demo under the instruction of swiftwasm-book. And I found the hello.wasm is very big ( >10MB ）。
I think the main reason is that print will be linked to libswiftCore， which size is 9MB。
AFAK, wasi in wasm is just stubs, it is dynamicly linked at runtime. So I'm trying to exclude these at linkage, by using --allow-undefined / --allow-undefined-file=undefined-symbols.txt after wasm-ld. But it doesn't work, error is:

wasm-ld: error: /tmp/hello-fcefd1.o: undefined symbol: $sSSN

I don't know how to resolve this, anyone help?

[MaxDesiatov]

Hi @didi11641, thanks for reporting the issue. As far as I know, neither WebAssembly, nor WASI support dynamic linking, and we don't do any dynamic linking at runtime. Both libswiftCore and WASI are linked statically and are required for SwiftWasm apps to work. libswiftCore contains the standard library and runtime, while WASI and ICU contain basic memory allocation and string manipulation code.

We have more details available about the ongoing effort to reduce the binary size in the related thread in the main SwiftWasm repository. Does that answer your question?

[didi11641]

@MaxDesiatov Thanks for your reply. I have looked into print implementation in Print.swift, I guess it will finally call funcs like _swift_stdlib_write in LibcShims.h ，which calls WASI API write。 Thanks for providing the related thread, I will keep track on that issue :)

[MaxDesiatov]

Closing this, as the binary size issues are tracked separately in swiftwasm/swift#7.