查看中的函数 _M_check_len c> bits / stl_vector.h 。它包含：

Look at the function _M_check_len in bits/stl_vector.h. It contains:

const size_type __len = size() + std::max(size(), __n);

因此，当追加n个元素时，基本策略要么加倍，要么增加n，最大。 pop_back 永不解除分配。 libc ++（LLVM）的作用完全一样。

So the basic strategy when you append n elements is either double the size or increase by n, whichever is largest. pop_back never deallocates. libc++ (LLVM) does exactly the same.

读取代码是唯一能找到字符串，释放等策略的方法。

Reading the code is the only way you'll find out the strategies for string, deallocation, etc.