[fpc-devel] property syntax extension

[Mattias Gaertner]

On Sun, 21 Oct 2007 08:36:24 +0200 (CEST)
Daniël Mantione <daniel.mantione at freepascal.org> wrote:

> 
> 
> Op Sun, 21 Oct 2007, schreef Michael Van Canneyt:
> 
> > > > .ppu file format is something so general and 
> > > > commonly used by (Free) Pascal programmers that 
> > > > it should become part of our RTL.
> > > 
> > > And another:
> > > A lazarus built with fpc 2.0.4 should be able to read the ppu of
> > > 2.3.x. Even though the ppu format is very stable, it is not
> > > carved in stone.
> > 
> > It's built so that a newer version can always read an older PPU file
> > and vice versa: an old ppu unit can read a newer file, but just
> > doesn't know how to interpret certain blocks.
> 
> This is not true. Take for example:
> 
>     procedure tarraydef.ppuwrite(ppufile:tcompilerppufile);
>       begin
>          inherited ppuwrite(ppufile);
>          ppufile.putderef(_elementdefderef);
>          ppufile.putderef(rangedefderef);
>          ppufile.putaint(lowrange);
>          ppufile.putaint(highrange);
>          ppufile.putsmallset(arrayoptions);
>          ppufile.writeentry(ibarraydef);
>       end;
> 
> If the arrayoptions for example becomes a large set (>32 elements), an
> old version that will try to read a new version will read too little 
> data. We will of course bump the ppu version, so the compile refuses
> old ppus. 

Is the newer ppureader be able to read older ppu?
In other words: Does a current ppureader contains the code to read the
old format too?


Mattias