sizeof（）std :: vector（C ++） [英] sizeof() std::vector (C++)

问题描述

这个主题已经有一个主题，但我仍然怀疑。要计算向量的大小，哪个正确：

There is a topic already on this topic but I have doubts still. To calculate the size of a vector, which one is correct:

sizeof(VEC) + sizeof(int) * VEC.capacity()

或

VEC.capacity() * (sizeof(VEC) + sizeof(int))

推荐答案

向量的大小是什么意思？向量对象的大小只是

What do you mean by size of the vector? The size of the vector object is just

sizeof(vec);

如果您对向量在堆上分配了多少内存感兴趣，可以使用

If you are interested in how much memory the vector has allocated on the heap, you can use

vec.capacity()*sizeof(T)

所以，如果你添加这些，你会得到多少内存你已经失去因为向量。

So, if you add these, you'll get how much memory you've "lost" because of the vector.

vec.capacity()*sizeof(T) + sizeof(vec)

$ b b

请注意，确切分配多少内存是依赖于实现的。这只是上面的公式将在大多数（如果不是所有实现）上实际上实际上正确（或大致正确）。

Please note that exactly how much memory is allocated is implementation-dependent. It's just that the formula above will be practically correct (or approximately correct) on most if not all implementations.

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