experimental :: basic_string_view <>是否适用于rvalues？

Question

I am not 100% that the following code is semantically correct:

#include <iostream>
#include <experimental/string_view>

int main()
{
    std::string str = "lvalue string";

    std::experimental::string_view view_lvalue(str);
    std::experimental::string_view view_rvalue(std::string{"rvalue string"});

    std::cout << view_lvalue << '\n' << view_rvalue << '\n';
}

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Question: Can I legally bind a rvalue to std::experimental::basic_string_view , or is it just UB? If yes, how does it work? As far as I know, a rvalue does not bind to a const reference (which I assume the view holds to the original string) via the constructor, so I thought that at the end of the statement std::experimental::string_view view_rvalue(std::string{"rvalue string"}); the reference will be dangling. Does string_view use a more sophisticated approach?

I am asking this because I am trying to write a similar view for some matrix class, and don't yet know how to deal with rvalues (I can disable them of course, but I don't think it's the best approach).

Answer 1

If cpprefernce is correct then this is UB. std::string_view has

A typical implementation holds only two members: a pointer to constant CharT and a size .

And the constructor has

Constructs a view of the first str.size() characters of the character array starting with the element pointed by str.data() .

So if string_view just points to the underlying char array of the provided string then we will have a dangling pointer once the expression ends and the temporary is destroyed.

As pointed out in the comments one reason this behavior may have been allowed is so you can pass a string_view to a function and construct that string_view from a temporary string