copyable-function

Technical analysis of the interconversion between std::function and std::copyable_function in C++26, discussing implementation approaches and performance trade-offs, with specific note that libstdc++ currently uses a less optimal approach.

C++26 introduces two new function wrappers: std::copyable_function, which provides a copyable, const-correct alternative to std::function, and std::function_ref, a non-owning callable reference with reference semantics.