Let’s continue our exploration of C++26 improvements. Today we focus on string_view. Some types got new constructors accepting string_views, and concatenation of strings and string_views just got easier.

C++26: string and string_view improvements

by Sandor Dargo

From the article:

But let’s start with a brief reminder of what a string_view is.

Reminder: the role of string_view

std::string_view was introduced in C++17 and its purpose is to provide read-only access to a string-like object. It can often replace const string& parameters and offers a significant performance gain. It’s generally advisable to use it whenever you’d pass an immutable string-like input that you cannot move from source to target.

We covered the topic earlier in more depth here.

P2495R3: Interfacing stringstreams with string_view

A stringstream is a good old tool for dealing with operations on string-based streams. While C++23 introduced spanstreams, due to fundamental semantic differences, stringstreams are not dead and it’s important to maintain them.

Being a good old tool also means they predate string_view. Given the available set of constructors, if you want to initialize a stringstream from a string_view, you first have to manually convert it into a string.

P2495R3 fixes this by adding new constructors accepting string_views.

It’s worth noting that this is a purely additive library change — it doesn’t break existing code.

At the moment of publication, this change is already available on Clang 19.