The State Of C++20 Features In GCC's libstdc++

With GCC 9 being released in just a short time and being now onto the final stage of development, besides fixing regressions the developers are also getting the documentation in order.

As part of getting the documentation squared away for the upcoming GCC 9.1 release, committed today was the documentation showing the status of the C++20 support within their libstdc++ C++ standard library.

Besides the GNU Compiler Collection itself moving along with its preliminary C++20 features, the libstdc++ library has also been working to stay in-step as new functionality gets worked out for this next planned update to the C++ programming language.

As implied by the name, with C++20 not coming out for another year at least, GCC 9.1 obviously won't have full support for it yet with various technical specifications still being discussed. C++20 is bringing many changes like ranges, a revised memory model, potentially modules / coroutines / transactional memory, and other additions.

On the library side, committed today was the current look at libstdc++ support. That new documentation added can be viewed here.

It shows that for GCC 9.1, libstdc++ picked up some library features like string prefix and suffix checking, remove_cvref transformation trait, integral power-of-2 operations, improving the return value of erase-like algorithms, efficient sized delete for variable sized classes, std::is_constant_evaluated(), and other additions.

But a majority of the planned C++20 library technical specifications remain yet to be implemented. Look for more of the C++20 support from the compiler and standard library to be fleshed out for next year's GCC 10 release. The experimental support in GCC 9 can be tapped with the -std=c++2a switch.