对 C++ 动态内存分配的确切含义有点困惑

Dynamic storage

Dynamic storage variables are controlled by developer. When you need them, you request the memory (usually with malloc in C or new in C++) and you must give it back when you no longer need it (with free in C, delete in C++). As a developer, you should be paying all attention in how you allocate, use and delete those, and make sure the sequence is never broken. Failure to observe the sequence is a single major cause of all the great program bugs making the news :). Luckily, C++ has special features and classes for you that simplify this task, but if you develop in C, you are on your own. In the example below, memory to where var4 points is dynamically allocated.

代码:

void foo() {
   int* var4;
   // Here is the major source of confusion. var4 itself is **automatic**
   // you do not need to allocate or free var4 memory, so you can use it
   // like this:
   var4 = NULL; // Not an error!!!
   // However, you can't use the memory var4 points to yet!
   // Following line would cause incorrect behavior of the program:
   // *var4 = 42; // NEVER EVER!!!
   // Instead, you need to allocate the memory first (let's assume, we are in C++
   var4 = new int();
   // Now the memory was allocated, we can use it
   *var4 = 42; // Correct!
   // we no longer need this memory, so let's free it:
   delete var4;
   // This did not change var4 itself (unless there is a special case)
   // so technically, it still points to the memory which was former 
   // belonging to you. But the memory is no longer yours!!!
   // you can't read or write it!
   // Following code is bad-bad-bad:
   // int x = *var4; // NEVER EVER! 
}

如您所见，使用动态内存伴随着最谨慎和警告标志.这就是为什么在 C++ 中有一些特殊的工具可以让这变得更容易，并且没有人会编写我上面写的代码.但是，我的帖子已经方式太长了，所以 C++ 中的适当内存管理将留待其他场合 :)