Link-time optimization
draft: cppreference PImpl # Runtime overhead
Access overhead: In pImpl, each call to a private member function indirects through a pointer. Each access to a public member made by a private member indirects through another pointer. Both indirections cross translation unit boundaries and so can only be optimized out by link-time optimization. Note that OO factory requires indirection across translation units to access both public data and implementation detail, and offers even fewer opportunities for the link time optimizer due to virtual dispatch.