[whizzter]

Where are we with modules, isn't pimpl there largely to avoid costs related to including the world?

I was pondering on why he was putting the defaulted methods in the cpp, any particular reasons?

I did realize that the indirect version is required to be in the cpp since the header won't know how to copy without knowing the definition of the impl class.

[pjmlp]

Even with modules, if you expose such types over the ABI, naturally the machine code memory layout will change, this is an issue regardless of the language.

[binary132]

The article explains why, indirect and unique_ptr are templated and require the complete definition of the type, and the default impls of those methods use methods of the templated types.

[ghosty141]

pimpl helps more since its trivially implementable in existing codebases while modules are a much bigger pain.

[knorker]

pimpl also makes it much easier to make changes without breaking ABI. E.g. shared libraries.

[cemdervis]

pimpl also helps to keep data structure layout stable, e.g. Qt's d-pointer convention