std::vector<some_class_type> vec; vec.reserve(10); some_class_type* ptr = vec.data() + 3; // that object doesn't exist yet
请注意,我没有尝试访问指向的值.
这是标准对data()的说明,但我不确定它是否相关：
Returns: A pointer such that
[data(),data() + size())is a valid
range. For a non-empty vector,data() == &front().
解决方法
23.3.6.3/2(重点是我的)
Effects: A directive that informs a vector of a planned change in size,so that it can manage the storage allocation accordingly. After reserve(),capacity() is greater or equal to the argument of reserve if reallocation happens; and equal to the prevIoUs value of capacity() otherwise. Reallocation happens at this point if and only if the current capacity is less than the argument of reserve()@H_403_26@. If an exception is thrown other than by the move constructor of a non-CopyInsertable type,there are no effects.
然而,如果您在添加足够的元素之前尝试取消引用指针,其中指针位于data()size()之外,或者如果添加多于capacity()),则会发生未定义的行为.
