Is the pImpl idiom really used in practice?

Question

I am reading the book \"Exceptional C++\" by Herb Sutter, and in that book I have learned about the pImpl idiom. Basically, the idea is to create a structure for the p

Answer 1

As many other said, the Pimpl idiom allows to reach complete information hiding and compilation independency, unfortunately with the cost of performance loss (additional pointer indirection) and additional memory need (the member pointer itself). The additional cost can be critical in embedded software development, in particular in those scenarios where memory must be economized as much as possible. Using C++ abstract classes as interfaces would lead to the same benefits at the same cost. This shows actually a big deficiency of C++ where, without recurring to C-like interfaces (global methods with an opaque pointer as parameter), it is not possible to have true information hiding and compilation independency without additional resource drawbacks: this is mainly because the declaration of a class, which must be included by its users, exports not only the interface of the class (public methods) needed by the users, but also its internals (private members), not needed by the users.