无法将 unsafe.Pointer（指向 C 函数）作为函数调用

Question

我正在尝试调用具有相同签名的 C 函数，它们采用 2 个 int 参数。这个错误 cannot call non-function f (type unsafe.Pointer) 出现在编译过程中。

package main

/*
int add(int a, int b) {
  return a+b;
}
int sub(int a, int b) {
  return a-b;
}
*/
import "C"
import (
    "fmt"
    "unsafe"
)

func main() {
    a := C.int(1)
    b := C.int(2)
    fx := make([]unsafe.Pointer, 2)
    fx[0] = C.add
    fx[1] = C.sub
    for _, f := range fx {
        fmt.Printf("Result: %d\n", f(a, b))
    }
}

现在我正在使用 go 函数包装 C 函数并将 go 函数添加到 slice 中，而不是像这样

package main

/*
int add(int a, int b) {
  return a+b;
}
int sub(int a, int b) {
  return a-b;
}
*/
import "C"
import (
    "fmt"
)

func add(a, b int) int {
    return (int)(C.add(C.int(a), C.int(b)))
}

func sub(a, b int) int {
    return (int)(C.sub(C.int(a), C.int(b)))
}

func main() {
    fx := [](func(int, int) int){
        add, sub,
    }
    for _, f := range fx {
        fmt.Printf("Result: %d\n", f(1, 2))
    }
}

有什么方法可以从 unsafe.Pointer 调用 C 函数，我使用的是 GO 1.8.1 Linux

Answer 1

我可以根据Go references to C解决我的问题。

Calling C function pointers is currently not supported, however you can declare Go variables which hold C function pointers and pass them back and forth between Go and C. C code may call function pointers received from Go.

看来我必须创建一个 bridge function 来调用 C 函数指针

package main

/*
int add(int a, int b) {
  return a+b;
}
int sub(int a, int b) {
  return a-b;
}

typedef int(*math_fp)(int, int);

const int len_operator = 2;

math_fp math_operators[2] = {
    add, sub
};

int do_math(math_fp op, int a, int b) {
    return op(a, b);
}
*/
import "C"
import (
    "fmt"
)

func main() {
    var fnCnt C.int = 2
    var i C.int
    for i = 0; i < fnCnt; i++ {
        op := C.math_fp(C.math_operators[i])
        fmt.Printf("Result: %d\n", C.do_math(op, 1, 2))
    }
}

Return 预期结果

$ go run src/test.go 
Result: 3  
Result: -1

无法将 unsafe.Pointer（指向 C 函数）作为函数调用

Unable to Call unsafe.Pointer(Pointed to C Function) as Function

go

cgo