第二种情况不是内存泄漏。

这不是一个泄漏，因为你仍然有一个指向分配的内存的指针。

要定义内存泄漏，我想坚持定义哪些大多数内存分析工具，如valgrind使用：

Second case is not a memory leak.
It is not a leak because you still have an pointer to the memory that was allocated.
To define a memory leak I would like to stick to definition which most of memory analysis tools like valgrind use:

内存已分配，不能随后释放，因为程序不再有任何指针到分配的内存块。

Memory was allocated and cannot be subsequently freed because the program no longer has any pointers to the allocated memory block.