How to generate shared wasm file with dylink.0 section

[ApsarasX]

Clang and Emscripten both could generate shared/PIC wasm file using the following commands.

clang --target=wasm32-unknown-emscripten -nostdlib -Wl,--shared -fPIC demo.c  -o demo.wasm

emcc demo.c -Os -s WASM=1 -s SIDE_MODULE=1 -o demo.wasm

So how does binaryen generate shared wasm file with dylink.0 section?

[kripken]

Binaryen support for the dylink section is here: (this is the binary writing part)

binaryen/src/wasm/wasm-binary.cpp

Line 1126 in b337a11

void WasmBinaryWriter::writeDylinkSection() {

I believe how it all works together is that passing SIDE_MODULE to emcc will make emcc call wasm-ld with --experimental-pic -shared. Then a dylink section is emitted. Binaryen work afterwards (wasm-emscripten-finalize, wasm-opt) will then read it and write it.

[ApsarasX]

Does Binaryen have to rely on emcc to emit a dylink section?

Can't Binaryen itself emit a dylink section?

Sorry, maybe I didn't make my application scenario clear.

I am using AssemblyScript based on Binaryen to generate wasm.

And I need to generate a main wasm module and a side wasm module(as dynamic link library, just like .so file) both running on my custom wasm runtime.

I'm looking for some methods in Binaryen that have the same effect as -experimental-pic -shared, but so far no luck.

[kripken]

Internally that is possible, basically this data structure should be filled out:

binaryen/src/wasm.h

Lines 1964 to 1965 in 0b0581a

	// Optional user section IR representation.
	std::unique_ptr<DylinkSection> dylinkSection;

However AssemblyScript uses Binaryen through binaryen.js, and I don't think we have a JS or C API for that yet. That would need to be added first, I think.