c++ - 为什么 std::array::front 和 std::array::back 不是 noexcept？

Question

我不熟悉 noexcept 说明符的使用，我不明白为什么 std::array::front 和 std::array: :back 未声明 noexcept (而 std::array::begin 和 std::array::end 是) .

这是什么原因？

Answer 1

来自 cppreference

There is a special case for a zero-length array (N == 0). In that case, array.begin() == array.end(), which is some unique value. The effect of calling front() or back() on a zero-sized array is undefined.

所以既然我们可以有一个 0 大小的数组 front() 和 back() 可能会导致异常

引用 Sebastian Redl在 why the standard doesn't mandate operator[], front and back be marked noexcept

The standard's policy on noexcept is to only mark functions that cannot or must not fail, but not those that simply are specified not to throw exceptions. In other words, all functions that have a limited domain (pass the wrong arguments and you get undefined behavior) are not noexcept, even when they are not specified to throw.