load wasm that build with golang

[bonly]

Thanks for the bug report!

Describe the bug

when I build wasm with go and wasm.NewInstance from the wasm bin, error result with:

Failed to compile the module.

A clear and concise description of what the bug is.

Steps to reproduce

1. build wasm with go
   GOARCH=wasm GOOS=js go build -o wa.wasm wa.go
   cat wa.go:

package main

//export Sum
func Sum(x, y int) int {
	return x + y
}

func main() {
}

2. build go program
   go build main.go
   cat main.go:

package main

import (
	"fmt"
	wasm "github.com/wasmerio/go-ext-wasm/wasmer"
)

func main() {
	bytes, err := wasm.ReadBytes("wa.wasm");
	if err != nil{
		fmt.Println(err);
		return
	}
	inst, err := wasm.NewInstance(bytes);
	if err != nil{
		fmt.Println(err);
		return
	}
	defer inst.Close();

	sum := inst.Exports["sum"]

	result, err := sum(5,37);
	if err != nil{
		fmt.Println(err);
		return;
	}
	fmt.Println(result);
}

3. Run

./main

4. See error
   Failed to compile the module.

[syrusakbary]

This is likely to be happening because some of the required imports are not present.

We probably need to improve the error message to show the detailed error.

[Hywan]

Thanks for the bug report!
Error messages are already better in the next runtime release, see https://github.com/wasmerio/wasmer/pull/467/files.

However, maybe you can find a better definition with wasm.GetLastError. I tried with the following code:

package main

import (
	"fmt"
	wasm "github.com/wasmerio/go-ext-wasm/wasmer"
)

func main() {
	bytes, err := wasm.ReadBytes("wa.wasm")

	if err != nil {
		fmt.Println(err)
		return
	}

	inst, err := wasm.NewInstance(bytes)

	if err != nil {
		fmt.Println(err)
		fmt.Println(wasm.GetLastError())
		return
	}

	defer inst.Close()
}

Then I run it with go run main.go and got:

Failed to compile the module.
7 link errors: (1 of 7)
Import not found, namespace: go, name: runtime.wasmExit (2 of 7)
Import not found, namespace: go, name: runtime.wasmWrite (3 of 7)
Import not found, namespace: go, name: runtime.nanotime (4 of 7)
Import not found, namespace: go, name: runtime.walltime (5 of 7)
Import not found, namespace: go, name: runtime.scheduleTimeoutEvent (6 of 7)
Import not found, namespace: go, name: runtime.clearTimeoutEvent (7 of 7)
Import not found, namespace: go, name: runtime.getRandomData <nil>

I suggest to use NewInstanceWithImports but imported function are declared in the env namespace, not in the go namespace. That's a missing feature currently.

[Hywan]

See #29 to see how to import functions in multiple namespaces.

[Irooniam]

Hi @Hywan can you provide a quick example how to import functions into multiple namespaces?

Like the parent, I tried running a go-compiled "hello world" wasm, and I get the following:
instance Failed to compile the module. 18 link errors: (1 of 18) Import not found, namespace: go, name: debug (2 of 18) Import not found, namespace: go, name: runtime.wasmExit (3 of 18) Import not found, namespace: go, name: runtime.wasmWrite (4 of 18) Import not found, namespace: go, name: runtime.nanotime (5 of 18) Import not found, namespace: go, name: runtime.walltime (6 of 18) Import not found, namespace: go, name: runtime.scheduleTimeoutEvent (7 of 18) Import not found, namespace: go, name: runtime.clearTimeoutEvent (8 of 18) Import not found, namespace: go, name: runtime.getRandomData (9 of 18) Import not found, namespace: go, name: syscall/js.stringVal (10 of 18) Import not found, namespace: go, name: syscall/js.valueGet (11 of 18) Import not found, namespace: go, name: syscall/js.valueSet (12 of 18) Import not found, namespace: go, name: syscall/js.valueIndex (13 of 18) Import not found, namespace: go, name: syscall/js.valueSetIndex (14 of 18) Import not found, namespace: go, name: syscall/js.valueCall (15 of 18) Import not found, namespace: go, name: syscall/js.valueNew (16 of 18) Import not found, namespace: go, name: syscall/js.valueLength (17 of 18) Import not found, namespace: go, name: syscall/js.valuePrepareString (18 of 18) Import not found, namespace: go, name: syscall/js.valueLoadString <nil>

Any help would be appreciated.

[Hywan]

You can check https://github.com/wasmerio/go-ext-wasm/blob/722faa9f1b902d404e87c40ea2bb6bdd5e228a51/wasmer/test/imports.go#L36-L52.

Basically, it looks like:

imports, _ :=
	wasm.NewImports().
		Namespace("env1").
			Append("f", f, C.f).
			Append("g", g, C.g).
		Namespace("env2").
			Append("h", h, C.h)

instance, _ := wasm.NewInstanceWithImports(wasm_bytes, imports)
…

Does it help?

[pkieltyka]

is it not possible for wasmer to parse out the imports when it reads the bytes and creates the instance? our nodejs version is able to load our wasm bytes just fine..

[Hywan]

It is possible to read the imports and exports from the module. Check the Module structure:

type Module struct {
    Exports []ExportDescriptor
    Imports []ImportDescriptor
}

[rusenask]

Hello, I am new to wasm and just trying out wasmer go-ext-wasm. Getting the same one

8 link errors: (1 of 8) Import not found, namespace: go, name: debug (2 of 8) Import not found, namespace: go, name: runtime.wasmExit (3 of 8) Import not found, namespace: go, name: runtime.wasmWrite (4 of 8) Import not found, namespace: go, name: runtime.nanotime (5 of 8) Import not found, namespace: go, name: runtime.walltime (6 of 8) Import not found, namespace: go, name: runtime.scheduleTimeoutEvent (7 of 8) Import not found, namespace: go, name: runtime.clearTimeoutEvent (8 of 8) Import not found, namespace: go, name: runtime.getRandomData

And I see that the issue is closed with that example:

imports, _ :=
	wasm.NewImports().
		Namespace("env1").
			Append("f", f, C.f).
			Append("g", g, C.g).
		Namespace("env2").
			Append("h", h, C.h)

instance, _ := wasm.NewInstanceWithImports(wasm_bytes, imports)

But I am still not sure how does this help? What are these and where they are coming from?

Namespace("env1").
			Append("f", f, C.f).
			Append("g", g, C.g).
		Namespace("env2").
			Append("h", h, C.h)

Is there anything specific that we need to do before running Go? Tried tinygo and go, both have slightly different errors :|

[Hywan]

The Go compiler emits a WebAssembly module with specific host functions (imports). It is very JavaScript centric.

The TinyGo compiler emits a WebAssembly module that works for JS but also other hosts, like a server.

See #95, which is likely to help.

One question though: What's your usecase to compile Go to Wasm, to then run it in Go?

[rusenask]

Currently writing a side project for my other side project (https://webhookrelay.com/) that will allow users to upload their wasm code snippets to modify webhooks before they are forwarded to their final destination. Initially started just with Lua but wasm seems so much more interesting, therefore after some time I decided to try out wasmer :)

For example to modify webhook method when it comes as a PUT request to POST:

extern "C" {
    fn ext_set_request_method(ptr: *const u8, len: usize);
}

#[no_mangle]
pub extern fn handleRequest(_ptr: i32, _len: i32) {
    
    let method = "POST";
    unsafe {
        ext_set_request_method(method.as_ptr(), method.len());
    }
}

As a Go developer myself I would prefer using Go, although Rust is also fun, not sure about other people though :)

[danlaine]

@Hywan Hello! So if I understand correctly there's no way to import a .wasm file that was compiled from Go. Is that right?

[Hywan]

@danlaine It is possible, but it requires some jugglery. Take a look at #95 for an attempt to simplify this.