[fpc-devel] class abstract, class sealed implementation. please review.

[Marco van de Voort]

In our previous episode, dmitry boyarintsev said:
> >> file, but the only they to see a full declaration is via documention,
> >> rather than header-sources.
> >
> > I don't understand this.
> 
> Delphi can compile a project with dcu present, but no .pas files.
> Any type or routine present in dcu can be used. The only problem of
> using them, is that there's no information in human-readable form
> about what actually presents in dcu.

FPC also, but has .ppu/.o.  (but harder to manage not giving source due a
multitude of questions.

But that is not related to the "external" question. The point is that the
.ppu have a defined state of a compilation step, with all the information
needed for the COMPILER.

This is different from linking to C/Obj C or other external sources where
you only have binary state after compiling the first part, enough for
the LINKER.
 
> Most of commercial components use this strategy: They do not provide
> sources, but they provide compiled .dcus (for any delphi version).
> With .dcu files they provide documentation over the component, so the
> user can see what classes, methods, functions or types are available,
> without need of studying sources.

No. .dcu is not a documentation format. The information is primarily for the
compiler, and .ppu contains the complete state needed for the compiler to
use that unit from another unit/prgram.  Rougly Delphi .dcu  folds in the
actual object code (.o) together with the unit info (.ppu) into one file