将Go指针传给Cgo

Question

我一直在玩GLFW绑定，我想通过GLFW向它传递一个Queue结构。SetUserPointer(…(，

因此，我通过了这样一个它：

type CircularQueue struct {
Values      []interface{}
Front, Rear int32
Capacity    int32
}
func newCircularQueue(capacity int32) *CircularQueue {
if capacity < 1 {
log.Fatal("Capacity of Circular Queue Zero or Negative")
}
queue := &CircularQueue{Capacity: capacity}
queue.Values = make([]interface{}, capacity)
return queue
}
...
events := newCircularQueue(16)
window.SetUserPointer(unsafe.Pointer(events))

但我遇到了一个运行时错误，

panic: runtime error: cgo argument has Go pointer to Go pointer

我做了一些挖掘，看起来。。。我引用：

Go code may pass a Go pointer to C provided the Go memory to which it 
points does not contain any Go pointers. The C code must preserve this 
property: it must not store any Go pointers in Go memory, even temporarily. 
When passing a pointer to a field in a struct, the Go memory in question is 
the memory occupied by the field, not the entire struct. When passing a 
pointer to an element in an array or slice, the Go memory in question is the 
entire array or the entire backing array of the slice. 

但是，我的结构中没有指针，我很困惑：(

Answer 1

解决方案非常简单。您必须将您提供给C代码的内容扁平化。与其传递循环队列，不如传递数据。

//C
int mysterious_c_func(const char* values, front int32_t, back int32_t, capacity int32_t);
// Go
type CircularQueue struct {
Values      []char //this can't possibly work with interface.
Front, Rear int32
Capacity    int32
}
...
var q CircularQueue
data := (*C.char)(unsafe.Pointer(q.values))
C.mysterious_c_func(data, C.int(queue.Front), C.int(queue.Rear), C.int(queue.Capacity))

但真正的问题是，您正试图部分用C实现复杂的数据结构，部分用Go实现。要么实现循环缓冲

1. 两种语言，并允许从数组构造
2. 只有在你真正需要这个概念的地方