golang "%p"学习记录随笔

　　对于获取slice的指针地址, 通过unsafe.Pointer 和 "%p"占位符两种方式得到的地址是不同的

　　

	s := make([]int, 1)
	t.Log(unsafe.Pointer(&s),unsafe.Pointer(&(s[0])),len(s),cap(s))
	t.Logf("%p\n",s)

　　unsafe.Pointer获取得到的是当前slice结构实例的指针

//runtime包下
type slice struct {
	array unsafe.Pointer
	len   int
	cap   int
}

　　

　　而"%p"获取到的是当前slice中存储的数组指针

// reflect包下的方法
func (v Value) Pointer() uintptr {
	// TODO: deprecate
	k := v.kind()
	switch k {
	case Chan, Map, Ptr, UnsafePointer:
		return uintptr(v.pointer())
	case Func:
		if v.flag&flagMethod != 0 {
			// As the doc comment says, the returned pointer is an
			// underlying code pointer but not necessarily enough to
			// identify a single function uniquely. All method expressions
			// created via reflect have the same underlying code pointer,
			// so their Pointers are equal. The function used here must
			// match the one used in makeMethodValue.
			f := methodValueCall
			return **(**uintptr)(unsafe.Pointer(&f))
		}
		p := v.pointer()
		// Non-nil func value points at data block.
		// First word of data block is actual code.
		if p != nil {
			p = *(*unsafe.Pointer)(p)
		}
		return uintptr(p)

	case Slice: // 这里获取的当前slice中存储的数组引用的内存地址
		return (*SliceHeader)(v.ptr).Data
	}
	panic(&ValueError{"reflect.Value.Pointer", v.kind()})
}