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From: ldo@waikato.ac.nz (Lawrence D'Oliveiro, Waikato University)
Newsgroups: comp.sys.mac.programmer
Subject: Re: MPW Linker wish...
Message-ID: <2533.27691409@waikato.ac.nz>
Date: 14 Dec 90 05:03:52 GMT
References: <2506.276672e0@waikato.ac.nz> <47309@apple.Apple.COM>
Organization: University of Waikato, Hamilton, New Zealand
Lines: 46

In <47309@apple.Apple.COM>, lins@Apple.COM (Chuck Lins) says

"An intelligent compiler will do [automatic ordering of initialization
code] at the module level. And there are techniques which ensure that
a module is initialized only once. Your compiler should be generating
code to do this."

I know, and it does. And I suspect nearly every Modula-2 compiler in
the world uses the same technique: call the initialization code for
*every* module you import, whether some other module imports it as
well or not; at the other end, the initialization routine maintains
a global flag which indicates if it's been called once or not, so
it can avoid repeating itself on subsequent calls. It's a helluva
hack, and it doesn't solve the circularity problem.

Actually, it's possible to extend this quite simply to detect
circularities, but you'll only pick them up this way when you come
to run the program, not at link time, which is when it should
be happening.

"...you've got to convince the MPW team that this is important.
Believe me, there's much more interest in Modula-2, etc outside
of Apple than within."

I didn't realize MPW was primarily meant as an in-house development
environment, but never mind.

"Ideally, the Make file should catch [out-of-date module symbol tables
and object code] and recompile for you."

Yes, but the Linker should also check, so that if I didn't get the
Makefile *quite* right, I'll have some explanatory messages to tell
me what went wrong, instead of a program that seems to build OK,
but just acts funny.

And finally, in a comment on my statement about the PDP-11 implementation
of Modula-2 being the original one:

"The original Modula-2 system was created on the Lilith by Prof. Wirth."

Yes, but he had to port it to the Lilith from somewhere...

Lawrence D'Oliveiro                       fone: +64-71-562-889
Computer Services Dept                     fax: +64-71-384-066
University of Waikato            electric mail: ldo@waikato.ac.nz
Hamilton, New Zealand    37^ 47' 26" S, 175^ 19' 7" E, GMT+13:00