Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!umd5!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: Makefile Maker
Message-ID: <9942@mimsy.UUCP>
Date: 23 Dec 87 22:58:17 GMT
References: <176@goofy.megatest.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 148
Keywords: make Makefile

In article <176@goofy.megatest.UUCP> djones@megatest.UUCP (Dave Jones) writes:
>... What you really want is something that keeps up with the
>dependencies automatically as they change. ... Let's cause the
>Makefile to update itself each time a dependency might have changed.

We already have something like this in 4.3BSD.  A number of the
makefiles in /usr/src support the command `make depend'.  Admittedly
this requires manual intervention---one has to decide that it is
time to update the dependency lists---but it works and is relatively
simple.

The makefiles distributed with 4.3BSD do this in an ugly way.  Each
makefile has something like this:

depend:
	for i in ${SUBDIR}; do (cd $$i; make ${MFLAGS} depend); done
	for i in ${STD} ${NSTD} ${SETUID}; do \
	    cc -M $$i.c | sed 's/\.o//' | \
	    awk ' { if ($$1 != prev) \
		{ if (rec != "") print rec; rec = $$0; prev = $$1; } \
		else { if (length(rec $$2) > 78) { print rec; rec = $$0; } \
		else rec = rec " " $$2 } } \
		END { print rec } '; done >makedep
	echo '/^# DO NOT DELETE THIS LINE/+2,$$d' >eddep
	echo '$$r makedep' >>eddep
	echo 'w' >>eddep
	cp Makefile Makefile.bak
	ed - Makefile < eddep
	rm eddep makedep
	echo '# DEPENDENCIES MUST END AT END OF FILE' >>Makefile
	echo '# IF YOU PUT STUFF HERE IT WILL GO AWAY' >>Makefile
	echo '# see make depend above' >>Makefile

# DO NOT DELETE THIS LINE -- make depend uses it

foo: foo.c /usr/include/stdio.h /usr/include/signal.h foo.h

# DEPENDENCIES MUST END AT END OF FILE
[etc]

As it happens, all the ugliness can be, should be, and as of a
number of months ago, has been, encapsulated in a program.  This
program is called `mkdep'; it is really just a shell script that
runs cc -M.  It has two options, `-f' (specify the name of the
makefile) and `-p' (producing programs: do the sed command shown
above, so that x depends on x.c and incl.h; otherwise x.o depends
on x.c and incl.h).

I am not sure I should post the script itself, but it is trivial,
since everything you need do is shown above.  Instead of the for
loop, mkdep assumes you are naming .c files, so the Makefile
entry now looks like this:

	depend: ldepend
		for i in ${SUBDIR}; do (cd $$i; make ${MFLAGS} depend); done

	ldepend:
		mkdep -p ${CFLAGS} ${CSRCS}

	# DO NOT DELETE THIS LINE -- mkdep uses it

	# DEPENDENCIES MUST END ... [etc]

(Here `depend' has been split to provide a `change local dependencies
only' target.  `make depend' in an upper-level source directory
such as /usr/src/ucb is time consuming, and deadly boring; `make
ldepend' confines dependency generation to the current directory.)

Disliking having to list both source files *and* programs (it seems
inelegant and error prone), I created two small scripts called
`addsuf' and `chgsuf', so that the `ldepend' target becomes

	ldepend:
		mkdep -p ${CFLAGS} `addsuf .c ${STD} ${NSTD}`

or

	ldepend:
		mkdep ${CFLAGS} `chgsuf .o .c ${OBJS}`

Since I wrote them, I know I can post them.  Here are addsuf and
chgsuf in their entirety:

#! /bin/sh
#
# addsuf - add suffix to each argument
# assumes no embedded spaces in arguments

case $# in 0) echo "usage: addsuf suffix files" 1>&2; exit 1;; esac

suf="$1"
shift
echo ${1+"$@"} | sed -e "s/ /$suf /g" -e "s/$/$suf/"

#! /bin/sh
#
# chgsuf - change suffix in each argument
# assumes no embedded spaces in arguments
# oldsuf is a string, not an R.E.

case $# in 0|1) echo "usage: chgsuf oldsuf newsuf files" 1>&2; exit 1;; esac

sed="sed -e s/[/.^[\*]/\\\\&/g"
oldsuf="`echo \"$1\" | $sed`"
newsuf="`echo \"$2\" | $sed`"
shift; shift
echo ${1+"$@"} | sed -e "s/$oldsuf /$newsuf /g" -e "s/$oldsuf$/$newsuf/"


Of course, there is still a problem for those for whom `cc -M'
produces nothing useful.  Fortunately, some time ago I wrote a
shell script for use on our Suns, which then did not support a -M
option for cc.  Not long ago I moved it to our Pyramid, which still
does not support cc -M (we run OSx release 2.5, as we have some
trouble getting current sources).  Here is that version:

#! /bin/sh
#
# getdep - get dependency lists.

# find cpp
cpp=/lib/cpp

# handle arguments
incl=
for i
do
	case "$i" in
	-I*)
		incl="$incl $i";;
	-O|-c|-M|-D*|-U*)
		;;
	*)
		# assume source file
		# put '$dep' in front of dependencies
		dep=`echo "$i" | sed -e 's,/,\\\\/,g' -e 's/\.c$/.o/'`
		# Find includes, remove leading numerics, remove ./,
		# remove double quotes, and remove trailing numerics.
		# Sort that, discarding duplicates, and add '$dep'.
		$cpp $incl "$i" | grep "^#" |
		sed -e 's/# [0-9]* //' -e 's,"./,",' -e 's/"\(.*\)"/\1/' \
		    -e 's/ [ 0-9]*$//' |
		sort -u | sed -e "s/^/$dep: /";;
	esac
done
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris