数据成员是否在与C ++中的对象相同的内存空间中分配？ [英] Are data members allocated in the same memory space as their objects in C++?

问题描述

说我有这样的类：

class Test
{
  int x;
  SomeClass s;
}

我像这样实例化：

Test* t = new Test;

堆栈上是x还是堆？

推荐答案

每次你使用一个新的实例化一个对象/符号将为此对象分配一个新的内存区域。

Each time you "instantiate" an object/symbol using a new (we are speaking C++ here), a new memory zone will be allocated for this object. If not, it will be put on the "local" memory zone.

问题是我没有本地内存区域的标准定义。

The problem is that I have no standard definition for "local" memory zone.

这意味着，例如：

struct A
{
   A()
   {
      c = new C() ;
   }

   B b ;
   C * c ;
}

void doSomething()
{
   A aa00 ;
   A * aa01 = new A() ;
}

对象aa00分配在堆栈上。

The object aa00 is allocated on the stack.

由于aa00 :: b根据aa00分配在本地存储器上，所以aa00 :: b分配在由新的aa01指令分配的存储器范围内。因此，aa00 :: b也在堆栈上分配。

As aa00::b is allocated on a "local" memory according to aa00, aa00::b is allocated inside the memory range allocated by the new aa01 instruction. Thus, aa00::b is also allocated on stack.

但aa00 :: c是一个指针，分配有new，所以由aa00 :: c设计的对象

But aa00::c is a pointer, allocated with new, so the object designed by aa00::c is on the heap.

现在，一个棘手的例子：aa01是通过一个新的分配，因此，在堆上。

Now, the tricky example: aa01 is allocated via a new, and as such, on the heap.

在这种情况下，由于aa01 :: b根据aa01分配在本地存储器上，aa00 :: b分配在由新的aa01指令分配的存储器范围内。因此，aa00 :: b在堆上，内部已经为aa01分配的内存。

In that case, as aa01::b is allocated on a "local" memory according to aa01, aa00::b is allocated inside the memory range allocated by the new aa01 instruction. Thus, aa00::b is on the heap, "inside" the memory already allocated for aa01.

由于aa01 :: c是一个指针，

As aa01::c is a pointer, allocated with new, the object designed by aa01::c is on the heap, in another memory range than the one allocated for aa01.

所以，游戏的点是：

1 - 被研究对象的本地内存是什么：Stack of Heap？

2 - 如果对象是通过new分配，那么它在这个本地内存之外，即它在堆上的其他地方

3 - 如果对象被分配没有新，则它在本地内存中。

4 - 如果本地内存在堆栈上，则分配的没有new的对象也在堆栈上。

5 - 如果本地内存在堆上，那么分配的没有new的对象也在堆上，但仍在本地内存中。

So, the point of the game is:
1 - What's the "local" memory of the studied object: Stack of Heap?
2 - if the object is allocated through new, then it is outside this local memory, i.e., it is elsewhere on the heap
3 - if the object is allocated "without new", then it is inside the local memory.
4 - If the "local" memory is on the stack, then the object allocated without new is on the stack, too.
5 - If the "local" memory is on the heap, then the object allocated without new is on the heap, too, but still inside the local memory.

对不起，我没有更好的词汇来表达这些概念。

Sorry, I have no better vocabulary to express those concepts.

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