panic: runtime error: invalid memory address or nil pointer dereference

Question

panic: runtime error: invalid memory address or nil pointer dereference

wwwAngHua opened this issue 2 months ago · comments

Problem description:

I used tinygo to compile a wasm file, and an error occurred when I used wasmer-go to read, compile and execute the file again.

Steps to reproduce

main.go

package main

import (
	"fmt"
	"os"

	"github.com/wasmerio/wasmer-go/wasmer"
)

func main() {
	engine := wasmer.NewEngine()
	store := wasmer.NewStore(engine)

	wasmBytes, err := os.ReadFile("test.wasm")
	if err != nil {
		fmt.Println("Error reading Wasm file:", err)
		return
	}

	module, err := wasmer.NewModule(store, wasmBytes)
	if err != nil {
		fmt.Println("Error compiling Wasm module:", err)
		return
	}

	instance, err := wasmer.NewInstance(module, nil)
	if err != nil {
		fmt.Println("Error instantiating Wasm module:", err)
		return
	}

	sumFunc, err := instance.Exports.GetFunction("sum")
	if err != nil {
		fmt.Println("Error getting function from Wasm module:", err)
		return
	}

	result, err := sumFunc(10, 20)
	if err != nil {
		fmt.Println("Error calling function from Wasm module:", err)
		return
	}

	fmt.Println("Result:", result)
}

wasm.go

package main

import (
	"syscall/js"
)

func sum(this js.Value, args []js.Value) interface{} {
	if len(args) != 2 {
		return "Invalid number of arguments. Expected 2."
	}

	num1 := args[0].Float()
	num2 := args[1].Float()
	result := num1 + num2
	return result
}

func main() {
	js.Global().Set("sum", js.FuncOf(sum))
	done := make(chan struct{}, 0)
	<-done
}

Expected behavior

The sum function exists and it should return the correct result.

Actual behavior

~/study/wasm tinygo build -o test.wasm -target wasm ./wasm.go

~/study/wasm go run main.go
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x10de47342]

goroutine 1 [running]:
github.com/wasmerio/wasmer-go/wasmer.(*ImportObject).intoInner(0x0, 0xc0000ca000)
        /Users/wanghua/go/pkg/mod/github.com/wasmerio/wasmer-go@v1.0.4/wasmer/import_object.go:36 +0x142
github.com/wasmerio/wasmer-go/wasmer.NewInstance(0xc0000ca000, 0x0)
        /Users/wanghua/go/pkg/mod/github.com/wasmerio/wasmer-go@v1.0.4/wasmer/instance.go:31 +0x45
main.main()
        /Users/wanghua/study/wasm/main.go:30 +0x149
exit status 2

JavaScript

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>Go WebAssembly Calculator</title>
    <script src="./wasm_exec.js"></script>
    <script>
      window.onload = function () {
        const go = new Go();
        WebAssembly.instantiateStreaming(
          fetch("./test.wasm"),
          go.importObject
        ).then((res) => {
          go.run(res.instance);
        });
      };

      function calculate() {
        const num1 = parseFloat(document.getElementById("num1").value);
        const num2 = parseFloat(document.getElementById("num2").value);
        console.log(window);
        const result = window.sum(num1, num2);

        document.getElementById("result").innerHTML = result;
        return new Promise(() => {});
      }
    </script>
  </head>
  <body>
    <h1>Simple Calculator</h1>

    <input type="number" id="num1" value="1" placeholder="Number 1" /> <br />
    <input type="number" id="num2" value="2" placeholder="Number 2" /><br />

    <button onclick="calculate()">Calculate</button>

    <h2>Result: <span id="result"></span></h2>
  </body>
</html>

Output:
Uncaught TypeError: window.sum is not a function at calculate (index.html:23:31) at HTMLButtonElement.onclick(index.html:36:35)

王华 · Answer 1 · Tue Mar 19 2024 09:59:00 GMT+0800 (China Standard Time)

package main

import (
	"fmt"
	"os"

	wasmer "github.com/wasmerio/wasmer-go/wasmer"
)

func main() {
	wasmBytes, _ := os.ReadFile("test.wasm")

	engine := wasmer.NewEngine()
	store := wasmer.NewStore(engine)

	// Compiles the module
	module, _ := wasmer.NewModule(store, wasmBytes)

	// Instantiates the module
	importObject := wasmer.NewImportObject()
	instance, _ := wasmer.NewInstance(module, importObject)

	// Gets the `sum` exported function from the WebAssembly instance.
	sum, _ := instance.Exports.GetFunction("sum")

	// Calls that exported function with Go standard values. The WebAssembly
	// types are inferred and values are casted automatically.
	result, _ := sum(5, 37)

	fmt.Println(result) // 42!
}

~/study/wasm go run main.go
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x10038efbd]

goroutine 1 [running]:
main.main()
        /Users/wanghua/study/wasm/main.go:24 +0x9d
exit status 2