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C++析构函数：什么时候释放内存？

发布于 2024-10-13 15:01:45 字数 58 浏览 4 评论 0原文

如果我删除一个导致其析构函数被调用的对象，那么内存是在析构函数完成函数中的任何操作之前还是之后被释放？

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給妳壹絲溫柔 2024-10-20 15:01:45

仅当最小派生类子对象被销毁后才会释放内存。因此，如果您有：

class Base {
};

class Derived : public Base {
public:
    ~Derived();
};

那么首先销毁Derived，然后销毁Base，然后才释放内存。

Memory is only freed once the least derived class subobject has been destroyed. So if you have:

class Base {
};

class Derived : public Base {
public:
    ~Derived();
};

then first Derived is destroyed, then Base is destroyed and only then memory is deallocated.

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路还长，别太狂 2024-10-20 15:01:45

将delete分解为它实际在做什么，可以比较清楚地看到内存什么时候被删除。所以像这样的语句：

delete some_ptr;

大致相当于这个伪代码：

some_ptr->~some_ptr();
free( some_ptr );

所以在调用析构函数后内存被释放。析构函数的确切作用不是由删除运算符决定的，而是由类的定义决定的。通常它会进行本地清理并确保其基类析构函数也被调用。

重要的是要认识到释放内存实际上并不是析构函数的一部分。释放内存的是delete操作符。

请注意，伪代码中的free 函数实际上是operator delete() 函数之一，无论是针对已删除的类，还是全局的。这实际上释放了内存。

Decompose delete into what it is actually doing and it is relatively clear to see when the memory is deleted. So a statement like this:

delete some_ptr;

Is roughly equivalent to this pseudo-code:

some_ptr->~some_ptr();
free( some_ptr );

So the memory is freed after the call to the destructor. Exactly what the destructor does is not determined by the delete operator, but rather the definition of the class. Usually it does local cleanup and ensures that its base class destructors are also called.

It is important to realize that freeing the memory is not actually part of the destructor. It is the delete operator which frees the memory.

Note that the free function in pseudo-code is actually one of the operator delete() functions, either for the deleted class, or global. That actually frees up the memory.

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