Re: Building an Ada compiler

[mfeldman@seas.gwu.edu (Michael Feldman)]

In article <4r0t56$50v@map.mda.ca>, Ray Blaak <blaak@mda.ca> wrote:
>erkodjk@aol.com (ErkoDJK) writes:
>
>>Some friends and I have a crazy idea.  We want to build an Ada 95 compiler
>>targeted for the Macintosh computer (without requiring Unix, like
>>GNAT/GCC).  
>
>Are you sure that GNAT requires UNIX? After all, its been ported to VMS and
>DOS. Change your project to that of porting GNAT, and most of your work is
>done.

GNAT does not, per se, require Unix, but it does require an underlying
GNU infrastructure (loader, assembler, machine descriptions and all that). 
The currently in-process GNAT for Mac uses MachTen as its host environment,
in part because MachTen provides a standard Unix shell and the necessary
GNU infrastructure. We looked at alternatives to MachTen, especially MPW,
but the necessary GNU stuff simply was not available. Same for MkLinux.

This GNAT is _hosted_ on MachTen, but _targets_ stand-alone Mac applications
as well. We are testing toolbox ("SDK") bindings, and in so doing have
already produced a number of quite decent Mac programs, with more to come.

True, MachTen is a partly proprietary environment, but so are MPW, 
CodeWarrior, Symantec, etc. The only completely free-software development
environment for Mac right now is MkLinux, which currently is supported
on only a limited range of Mavs (that limitation will change with time)
and does not coexist with other "ordinary" Mac apps. The nice thing
about MachTen is that it runs as a Mac app, so you can keep Word or Excel
(or whatever) running in another window.

It is commonly estimated that producing a GNAT port, given that the GNU
backend (machine-description) support already exists, takes about a
person-year. Given the existence of MachTen with its GNU support for
68k and PowerMac, this project is turning out to be roughly in that
ballpark.

See http://gnat-mac.com/macada/ for details. You can download GNAT
3.05, which is in pretty good shape. You do need MachTen, of course.

You might want to consider doing a GNAT port to MkLinux, or to MPW, if the
GNU stuff is available yet for MPW. I do NOT recommend starting from
scratch, unless you have lots of resources. 

Mike Feldman
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Michael B. Feldman -  chair, SIGAda Education Working Group
Professor, Dept. of Electrical Engineering and Computer Science
The George Washington University -  Washington, DC 20052 USA
202-994-5919 (voice) - 202-994-0227 (fax) 
http://www.seas.gwu.edu/faculty/mfeldman
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