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From: chris@nrcvax.UUCP (Chris Grevstad)
Newsgroups: comp.unix.questions,comp.unix.wizards
Subject: Strange makefile construct
Message-ID: <1162@nrcvax.UUCP>
Date: Wed, 2-Sep-87 02:21:12 EDT
Article-I.D.: nrcvax.1162
Posted: Wed Sep  2 02:21:12 1987
Date-Received: Sat, 5-Sep-87 14:00:40 EDT
Reply-To: chris@nrcvax.UUCP (Chris Grevstad)
Organization: Frobozo Items Co. Inc. Ltd.
Lines: 37
Xref: mnetor comp.unix.questions:3869 comp.unix.wizards:4069

I was looking at some source that came across the net some time ago and
ran across a very strange construct in the makefile.  It appears that this
makefile is targeted for a SYSV system and I am familiar only with 4.2BSD
make.

This is the weirdness:

target: file1.o file2.o file3.o file4.o
	$(CC) $(CFLAGS) $(?:.o=.c)

Any suggestions?  I'm hacking on the 4.3BSD make and wouldn't mind putting
this in, if it does what I think it does.

My interpretation says:
	This:
		$(CC) $(CFLAGS) $(?:.o=.c)
	becomes this:
		$(CC) $(CFLAGS) file1.c file2.c file3.c file4.c

If my interpretation is correct, then exactly what does $(?:.o=.c) mean?
Does the colon signify merely a modifier for the $? macro?  Or is it some
perversion of the standard colon dependency?  And is the equals sign a
special instance of the regular macro definition construct?  Or does it just
specify a transform of all elements in $? that terminate in .o?

As an aside, can someone enumerate some of the differences between the 4.3BSD
make and the Fourth Generation Make (or whatever they call it) from AT&T?

Any informed answers are gratefully anticipated.


-- 
	Chris Grevstad
	hplabs!sdcrdcf!psivax!nrcvax!chris
	ihnp4!nrcvax!chris

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