C++ 是否在清除时释放 std::vector 内存？
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Is std::vector memory freed upon a clear?
提问by Jerry Coffin
Suppose I have a std::vector of structs. What happens to the memory if the vector is clear()'d?
假设我有一个 std::vector 结构体。如果向量被 clear()'d，内存会发生什么？
std::vector<myStruct> vecs;
vecs.resize(10000);
vecs.clear();
Will the memory be freed, or still attached to the vecs variable as a reusable buffer?
内存会被释放，还是仍然作为可重用的缓冲区附加到 vecs 变量？
回答by Jerry Coffin
The memory remains attached to the vector. If you want to free it, the usual is to swap with an empty vector. C++11 also adds a shrink_to_fitmember function that's intended to provide roughly the same capability more directly, but it's non-binding (in other words, it's likely to release extra memory, but still not truly required to do so).
内存仍然附着在向量上。如果你想释放它，通常是用一个空向量交换。C++11 还添加了一个shrink_to_fit成员函数，旨在更直接地提供大致相同的功能，但它是非绑定的（换句话说，它可能会释放额外的内存，但仍然不是真正需要这样做）。
回答by Alexander Chertov
The vector's memory is not guaranteed to be cleared. You cannot safely access the elements after a clear. To make sure the memory is deallocated Scott Meyers advised to do this:
不保证会清除向量的内存。清除后您无法安全地访问元素。为了确保内存被释放，Scott Meyers 建议这样做：
vector<myStruct>().swap( vecs );
Cplusplus.comhas the following to say on this:
Cplusplus.com对此有以下说法：
Removes all elements from the vector, calling their respective destructors, leaving the container with a size of 0.
The vector capacity does not change, and no reallocations happen due to calling this function. A typical alternative that forces a reallocation is to use swap:...
从向量中移除所有元素，调用它们各自的析构函数，使容器的大小为 0。
向量容量不会改变，也不会因为调用这个函数而发生重新分配。强制重新分配的典型替代方法是使用交换：...
回答by Ryan Guthrie
The destructor is called on the objects, but the memory remains allocated.
对对象调用析构函数，但内存保持分配。
回答by BAK
No, memory are not freed.
不，内存没有被释放。
In C++11, you can use the shrink_to_fitmethod for force the vector to free memory.
在 C++11 中，您可以使用shrink_to_fit强制向量释放内存的方法。
