Re: [?] GNU g77 FORTRAN compiler witten in C?

Re: [?] GNU g77 FORTRAN compiler witten in C?

[Ralph Silverman]

Kaz Kylheku (kaz@helios.crest.nt.com) wrote:
: In article <danpop.878749765@news.cern.ch>, Dan Pop <Dan.Pop@cern.ch> wrote:
: >>The fact that the back end is written in C is a complication that may
: >>also encourage the use of C for the front end, but definitly does not
: >>force the use of C. Note that GNAT, the GNU Ada compiler, is written
: >>almost entirely in Ada (at one time I believe its only C code was a C
: >>main for compatibility with the back end).
: >
: >I can see two problems:
: >
: >1. How do I install it on my machine, which has no Ada compiler?
: >
: >2. How do I port it to a new architecture, which has no Ada compiler?
: >
: >The answer, in both cases, seems to be: find an Ada compiler written in C.

: The actual answer is that you get GNAT binaries to bootstrap yourself---the
: same way that you get GCC binaries with your Linux distribution or
: same way you get your C compiler from a commercial vendor.

: How would you port it to an architecture that has no Ada compiler? Once you
: have a GNAT development system running, you can retarget the Ada compiler you
: have. You can then compile programs for that previously unsupported platform.
: You then compile the compiler itself and get it running on that platform!
: (Easier said than done, of course, but in principle that is what you would do).
: -- 
: "In My Egotistical Opinion, most people's C programs should be
: indented six feet downward and covered with dirt."
: 	-- Blair P. Houghton

	unix os,
	originally designed to be
		portable
	faces similar problem ...
	generally,
	solved similarly ...

	and this works well,
	as many implementations
	of this,  and similar,
	systems shows ...
		aix
		hp-ux
		solaris
		ultrix
		sunos
		xenix
		coherent
		linux
		bsd
	etc. ...

--

Ralph Silverman
z007400b@bcfreenet.seflin.lib.fl.us

Re: [?] GNU g77 FORTRAN compiler witten in C?

[Robert Dewar]

Ralph said

<<: How would you port it to an architecture that has no Ada compiler? Once you
: have a GNAT development system running, you can retarget the Ada compiler you
: have. You can then compile programs for that previously unsupported platform.
: You then compile the compiler itself and get it running on that platform!
: (Easier said than done, of course, but in principle that is what you would do)>>

This is much more than theory. The above described approach has been 
successfully used to move GNAT to a large number of machines, including
many ports done by volunteers with zero help from the GNAT folks, e.g.
the DOS port appeared out of the blue this way, as did the Amiga port.
Yes, you need to know gcc reasonably well to do this, but there are lots
of people who know enough.

Originally we thought we would have to somehow address the issue of how
to port the system in a pure C manner, but in practice this has turned
out to be a non-issue. Indeed porting GNAT to a new target at the very
basic level of getting the compipler to run non-taskin programs is
pretty straightforward. The harder part is porting the tools and the
tasking.