C ++重新分配指针然后删除它

Question

Is this safe and correct? I mean does the delete care only about the address it is given or is it important to delete the original pointer variable?

myClass *p1 = new myClass();
myClass *p2 = p1;
delete p2;
p1 = NULL;
p2 = NULL;

Answer 1

删除只关心地址 ，因此您的代码完全合法。

Answer 2

Is this safe and correct?

It works . That is, it has well-defined behaviour and doesn't leak (assuming it compiles).

But safe? It is a dangerous idea to have aliased pointers running around free. You have to track which pointers have been deleted and which aren't; which point to memory that was deleted and which don't.

It's much safer to use RAII-enabled handles to manage your dynamically allocated objects, like std::unique_ptr and std::shared_ptr (or boost replacements). std::unique_ptr doesn't allow aliasing, and std::shared_ptr allows aliasing in a safe manner.

Answer 3

Since p1 and p2 point to the same object, then if you delete it through p2, you will also have deleted what pointed p1 to. So this is correct.

Answer 4

This is fine. You allocated memory to p1, then referenced the SAME memory in p2. When you called delete on p2, the memory that p1 was also deleted (they're the same thing, location and all). It's also correct that you set them both to NULL, as deleting p1 otherwise after that may have caused some problems since it was no longer pointing to valid memory.