C中的struct'type cast'错误？

Question

Suppose I have some struct DATA defined. Then I attempt the following code:

struct DATA data1, data2;
data2 = (DATA)(*(DATA))&data1);

Why do I get error C2440 on 'type cast'?

Answer 1

This part is the problem:

(DATA)&data1

Here you takes the address of data1 making into a pointer, type struct DATA * . Then you try to cast it to a non-pointer struct DATA type which is what the error is probably about. (Hint: Please post complete and unedited error messages in the future.)

You actually don't have to do any casting, or address-of pointer handling or dereferencing at all. Just assign one structure to the other, and the compiler will create code to do the proper copying:

data2 = data1;

Answer 2

The right thing to do is :

struct DATA data1, data2;
data2 = (struct DATA)(*((struct DATA*)&data1));

But this is useless... What not doing this :

struct DATA data1, data2;
data2 = data1;

Answer 3

It's illegal to cast to a struct type. The type specified by a cast operator must be either void or a scalar type (ie, an arithmetic or pointer type).

This:

data2 = data1;

is a much simpler way to do what I think you're trying to do (it's hard to tell).