[fpc-devel] property syntax extension

[Michael Van Canneyt]

On Sun, 21 Oct 2007, Mattias Gaertner wrote:

> On Sun, 21 Oct 2007 00:46:19 +0200 (CEST)
> Michael Van Canneyt <michael at freepascal.org> wrote:
> 
> > 
> > 
> > On Sat, 20 Oct 2007, Mattias Gaertner wrote:
> > 
> > > On Sat, 20 Oct 2007 16:29:40 +0200
> > > "Tomas Hajny" <XHajT03 at mbox.vol.cz> wrote:
> > > 
> > > > On 19 Oct 07, at 13:14, Micha Nelissen wrote:
> > > > > Jonas Maebe wrote:
> > > > > > This is not true. You can perfectly compile a compiler using
> > > > > > the previous' release rtl. 
> > > > > 
> > > > > Sure this is not the question.
> > > > > 
> > > > > > E.g. the people developing using the fp IDE often 
> > > > > > do this (because they have a project for the compiler, but
> > > > > > that one does not automatically compile the rtl). 
> > > > > 
> > > > > Adapt the project to use the new RTL ? Anyway, seems
> > > > > "dangerous" to me, not testing possible RTL regressions then.
> > > > > 
> > > > > > A while ago, Peter removed several 
> > > > > > dependencies of the compiler on the new rtl (related to endian
> > > > > > swapping routines) for this reason.
> > > > > 
> > > > > I see the reason is not really coming out, but I'll stop now.
> > > > 
> > > > Well, I'd certainly have one (more) reason not to 
> > > > put it into RTL - I don't think that support for 
> > > > .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.
> 
> Are we talking about a complete ppu parser or something to only read
> the property info?

Well, the ppu file is divided in blocks; Each block has a type and a 
size. If you don't "know" a block, you can 'skip' it.
(If memory serves me right, of course)

> 
>  
> > > So, maybe it would be best to keep a working copy of the ppu reader
> > > unit in the lazarus svn and give it a distinct name?
> > 
> > I think such a unit could best go in the packages, since it is
> > tightly bound to FPC, and definitely non-visual ? 
> 
> Well, it should be bound to FPC, but it should not be bound to a
> specific FPC version.

Exactly. That's why we need a copy. The copy (ppuparser or whatever)
can maintain knowledge of past versions, as far as that is needed.

Michael.