C++26: Deprecating or removing library features

In the previous article, we discussed what language features are removed from C++26. In this one, we are going to cover both language features that are finally removed after a few years of deprecation, and also those that are getting deprecated by C++26. As a reminder, a removal from the language usually happens in two steps. First a feature gets deprecated, meaning that its users would face compiler warnings for using deprecated features. As a next step, which in some cases never comes, the compiler support is finally removed. Remove Deprecated std::allocator Typedef From C++26 The std::allocator has a typedef that was deprecated in C++20 and now finally it’s removed. Though it’s a minor corner case, but it’s been so easy to misuse it that it was rather embarrassing for the committee, hence the removal by P2868R3. Classes deriving from std::allocator don’t synthesise the typedef member correctly and the allocator authors have to add their own typedef to ensure correct behaviour. I ... Read full article.