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From: jso@edison.UUCP (John Owens)
Newsgroups: mod.computers.vax
Subject: Re: main() and entry points in C
Message-ID: <8607071658.AA15798@edison.UUCP>
Date: Mon, 7-Jul-86 12:58:16 EDT
Article-I.D.: edison.8607071658.AA15798
Posted: Mon Jul  7 12:58:16 1986
Date-Received: Tue, 8-Jul-86 19:03:57 EDT
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I agree.  Certainly there are many UNIX programs that take advantage
of specific non-portable features!  I wish that more people would use
varargs, but old habits die hard.  varargs being a fairly recent
innovation, many people won't use it just because they're likely to
find more UNIX implementations that'll work the old way than those
with varargs, since everyone wants to stay compatible with existing
programs!

I finally went and read the start() routine, and was surprised to find
that it was written partially in C, with a few "asm" directives.  Many
other UNIX implementations, such as the PDP-11 ones, have this written
in assembler, with no public symbol for the first location.  (The name
_start comes from the fact that the C compiler prepends an underscore
to any external symbol.)

WRT mixing languages, I've found that just as cc will run as on any
assembler files, then invoke the loader appropriately, f77 will invoke
the c compiler on any .c files and the assembler on any .s files, etc.
The (admittedly ad-hoc) solution has usually been to have the
interface to your "new" langauge handle the linking with C modules,
and any others you know about.  Even without this, you can always do
something like:

	cc a.c b.c c.c
	f77 d.f e.f
	mod2 f.m g.m
 -- and then, if your main program is C, with Fortran and Modula-2 routines --
	cc a.o b.o c.o d.o e.o f.o g.o
 -- or if it's Fortran with C and Modula-2 routines --
	f77 a.o b.o c.o d.o e.o f.o g.o
 -- etc, since any interface should just pass .o files on to ld --

One of the things I actually liked about VMS (really!  it does have a
few redeeming qualities) was that all the langauge interfaces were
extremely standardized, to the point that the main rtl was common to
all languages.  Of course it didn't have to be so cumbersome an
interface....

		In hope of universitality-
			-John
			(edison!jso%virginia@CSNET-RELAY.ARPA)