Pitfalls of std::string_view

std::string_view is a powerful tool in C++, offering benefits such as efficient string handling without the overhead of copying. However, it comes with some pitfalls that developers need to be aware of.

One of the primary risks is dangling references. Since std::string_view does not own the underlying string, it can easily reference invalid memory if the original string is modified or destroyed. For example:

1#include <iostream>
2#include <string_view>
3
4int main() {
5  std::string_view view;
6  {
7    std::string str{"Hello, World!"};
8    view = std::string_view{str};
9  }  // str is destroyed here
10
11  std::cout << view;  
12}

1undefined behavior or runtime error

In this example, view points to a string that has been destroyed, leading to undefined behavior.

std::string_view does not ensure the underlying string is null-terminated. Functions expecting null-terminated strings, like many C APIs, can misbehave if passed a std::string_view:

1#include <iostream>
2#include <string_view>
3#include <cstring>
4
5int main() {
6  std::string_view view{"Hello"};
7  std::cout << std::strlen(view.data());  
8}

1undefined behavior

Here, view.data() may not point to a null-terminated string, causing std::strlen to read out of bounds.

std::string_view treats the underlying string as immutable. If you need to modify the string, you must convert it back to a modifiable type, such as std::string. This conversion incurs overhead and might not be efficient for frequent modifications.

Ensuring that the lifetime of the underlying string outlasts the std::string_view can be tricky, especially in complex applications. It's easy to accidentally reference a temporary string, leading to subtle bugs.

Despite its pitfalls, std::string_view is incredibly useful for efficient string handling.

However, developers must carefully manage the lifetime of the underlying string, avoid passing std::string_view to functions expecting null-terminated strings, and remember that std::string_view provides a read-only view.