On Thu, 27 Nov 2008, Marco van de Voort wrote:
> In our previous episode, Thaddy said: > > I remember that the Delphi to java bytecode compiler isn't feature > > complete. I can't be: it will not be possible to compile any old delphi > > program into java byte code for several reasons. But it is possible to > > create Java bytecode with a - safe - subset of pascal syntax. It is also > > possible to use the same intermediate compiler to compile to .net/mono, > > though. It isn't possible to adapt Freepascal to write once compile > > anywhere with Java OR .Net. Both these assume restrictions that are > > simply not there in native code compilers, so you would have to work > > with one lame leg. I hope you realize that. > > Besides the pure language problem, there is also the library problem. Java > and .NET are more than just a bytecode specification, there are also vast > standard libraries, and the VCL-alike standard libraries of FPC (classes > unit etc) are not designed to work on top of Java or .NET classes. > > So then you get a problem, what do you do? Keep it compatible with native, > but a bit alien to the Java or .NET world, or re-spin the libraries in a > more Java/.NET compatible way, building on top of the base libs. Also for > this a lot of language extensions must be implemented that might not be > elegantly back-portable to native, since their philosophies are not the > same. > > But if you do such step, you introduce such a big barrier to actually > switching between native and bytecode worlds (and probably between .NET and > Java too) that one must ask what the benefit of long term keeping it in the > same project really is. Since the native and bytecode targets basically then > only share the base parser and semantic analysis. > > This friction probably lead to the demise of VCL.NET and shared source on > the Borland side. > > As soon as you get the pure language part working, the users will fragment > over mostly native and mostly bytecode oriented, and the common ground is > gone. Well, I think that the compiler could be shared between a native code and bytecode machine. Jonas implemented something like it, so this part is possible. But: - The RTL and class libraries would be totally different, since, as you correctly point out, the Java/.Net world have different philosphies. (no pointers, etc.) This is the main problem, as it requires a large effort. - One should not attempt to implement Java or C# language constructs in Pascal. Michael. _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
