The PImpl idiom and the C++26 std::indirect type

PImpl (Pointer to Implementation) is a C++ idiom for hiding implementation details behind an opaque pointer to reduce compile-time dependencies. The post walks through three implementations: using raw pointers with the Rule of Five, using std::unique_ptr for automatic resource management, and using the new C++26 std::indirect type. std::indirect is a vocabulary type that owns a heap-allocated object but behaves like a value member — it supports deep copy, propagates const, and is never null except after a move (detectable via valueless_after_move()). Compared to unique_ptr, std::indirect makes PImpl implementations more robust by eliminating the constness propagation issue and providing a cleaner moved-from state check. Currently only GCC 16 supports std::indirect.

Nguồn: https://mariusbancila.ro/blog/2026/07/23/the-pimpl-idiom-and-the-cpp26-stdindirect-type. 8sync News chỉ tóm tắt và dẫn link; bản quyền nội dung thuộc tác giả và nguồn gốc.