3
struct a{
int a;
int b;
};
struct b{
int a;
int b;
}
int main()
{
struct a *p;
struct b b;
p = (struct a *)b; // deste modo da erro
p = (struct a *)&b; ; deste modo o compilador não aponta erro;
}
I’d like to know why?
2
(struct a *)b is taking a structure and making a cast for a pointer to a structure. This is not possible. A pointer is something very different from a structure.
In this case you are trying to put a structure with two integers inside a pointer and it does not fit. The main point of the type struct a * is that it is a pointer. What it points to is important, but secondary, primarily is a pointer.
(struct a *)&b is picking up an address for a structure, which is a pointer and making a cast for a pointer to a structure, this is possible. Are incompatible types, is pointer to pointer.
The & is the operator that picks up the address of something, that is, it generates a data that potentially will be a pointer, but will never be a structure.
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