为什么不vector :: clear从向量中删除元素？ [英] Why doesn't vector::clear remove elements from a vector?

问题描述

当我在 std :: vector 上使用 clear（）时，应该销毁所有元素

When I use clear() on a std::vector, it is supposed to destroy all the elements in the vector, but instead it doesn't.

示例代码：

vector<double> temp1(4);
cout << temp1.size() << std::endl;
temp1.clear();
cout << temp1.size() << std::endl;

temp1[2] = 343.5; // I should get segmentation fault here ....

cout << "Printing..... " << temp1[2] << endl;
cout << temp1.size() << std::endl;

现在，我应该在尝试访问已清除向量时得到分段错误，

Now, I should have gotten segmentation fault while trying to access the cleared vector, but instead it fills in the value there (which according to me is very buggy)

结果如下：

4
0
Printing..... 343.5
0

这是正常吗？

推荐答案

当你访问的边界外时，一个向量，你会得到未定义的行为。这意味着任何事情都会发生任何东西。

When you access outside of the bounds of a vector, you get Undefined Behavior. That means anything can happen. Anything.

所以你可以得到旧的值，垃圾或seg错误。

So you could get the old value, garbage, or a seg-fault. You can't depend on anything.

如果要进行边界检查，请使用 at（）成员函数 operator [] 。它将抛出异常而不是调用未定义的行为。

If you want bounds checking, use the at() member function instead of operator []. It will throw an exception instead of invoking Undefined Behavior.

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