2019-08-18 08:42
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I'm looking at wasmer go-ext-wasm example code /go-ext-wasm/wasmer/test/imports.go learning about setting context data. I want to pass a pointer as contextData, what's the best way to do this?

//export sum
func sum(context unsafe.Pointer, x int32, y int32) int32 {
    instanceContext := wasm.IntoInstanceContext(context)
    t := *(*int)(instanceContext.Data())
    log.Print("t: ", t)
    return x + y

func testInstanceImport(t *testing.T) {
    imports, err := wasm.NewImports().Namespace("env").Append("sum", sum, C.sum)
    assert.NoError(t, err)

    instance, err := wasm.NewInstanceWithImports(getImportedFunctionBytes("examples", "imported_function.wasm"), imports)
    defer instance.Close()
    assert.NoError(t, err)

    bar := int(2)
    barPtr := &bar

    data := unsafe.Pointer(&bar)
    log.Printf("bar %v, barPtr %v", bar, barPtr)
    add1, exists := instance.Exports["add1"]
    assert.Equal(t, true, exists)

    result, err := add1(1, 2)
    log.Print("Result: ", result)
    assert.Equal(t, wasm.I32(4), result)
    assert.NoError(t, err)

Which gives me the expected value of 2 for context in the sum function. However when I change data := unsafe.Pointer(&bar) to data := unsafe.Pointer(&barPtr) I get a: runtime error: cgo argument has Go pointer to Go pointer error.

It works when I run it with GODEBUG=cgocheck=0 Should I be concerned running with this flag? Is what I'm trying to do a bad idea? I have a struct that contains a pointer that I need to pass as contextData, is using the GODEBUG=cgocheck=0 a bad idea?

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1条回答 默认 最新

  • doupao5296 2019-08-19 07:40

    I found the solution here: cgo: Go pointers in Go memory The Registry Example (Alternative) solves my issue. Thanks.

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