Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!tank!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.wizards
Subject: Re: generating code to run multiple targets/configurations from single
Message-ID: <16877@mimsy.UUCP>
Date: 12 Apr 89 05:23:46 GMT
References: <3129@stpstn.UUCP> <18927@adm.BRL.MIL> <10445@bloom-beacon.MIT.EDU> <12741@swan.ulowell.edu>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 67

4.3BSD-tahoe introduced a `#define' in <machine/machparam.h> called
MACHINE; on the VAX it is

	#define MACHINE "vax"

and on the Tahoe it is

	#define MACHINE "tahoe"

The program /bin/machine is made from the source (slightly trimmed)

	#include <sys/machine.h>

	main()
	{
		puts(MACHINE);
		exit(0);
	}

and thus produces `vax', `tahoe', or whatever.

make(1) has a built-in macro ${MACHINE} which expands to whatever
make's source got out of <machine/machparam.h>, so Makefiles can
read

	# Makefile for /usr/src/etc
	...
	SUBDIR=	... etc.${MACHINE}

	all: ${PROGS} ${SUBDIR} ...

	${SUBDIR}: FRC
		cd $@; make ${MFLAGS}

In addition, make reads the file `.depend' as well as the file
`Makefile' (or `makefile'), so that automatic dependency genration need
not rewrite makefiles.  This is much nicer (and clearly the way it
should have been done originally).

Existing `make's can be made to do the same thing by superimposing a
front-end shell script.  Here is /usr/local/bin/make from our Suns.
(`machine' is found in /usr/local/bin and says `echo sun'.  This points
up a problem: `sun' is not always specific enough; some sources might
be Sun-2 specific and some might be Sun-3 specific.  A simple fix would
be to make it produce `sun2' or `sun3' and make bin.sun2 and bin.sun3
symlinks to bin.sun in /usr/src/local/bin; but it might be better to
have two levels, or perhaps more.)

#! /bin/sh

if [ -f .depend ]; then
	if [ -f makefile ]; then
		f="-f makefile -f .depend"
	else
		f="-f Makefile -f .depend"
	fi
	for i do
		case "$i" in -f*) f=;; esac
	done
else
	f=
fi

exec /bin/make $f ${1+"$@"} MACHINE=${MACHINE-`machine`}
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris