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From: Ruslan Ermilov <ru@freebsd.org>
Subject: Re: bin/61527: make -j2 changes $*
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The following reply was made to PR bin/61527; it has been noted by GNATS.

From: Ruslan Ermilov <ru@freebsd.org>
To: Albert Hofkamp <a.t.hofkamp@tue.nl>
Cc: freebsd-gnats-submit@freebsd.org
Subject: Re: bin/61527: make -j2 changes $*
Date: Sun, 18 Jan 2004 16:35:15 +0200

 On Sun, Jan 18, 2004 at 06:03:41AM -0800, Albert Hofkamp wrote:
 > 
 > with a make rule like
 > 
 > foo/bar.o: foo/bar.cc
 >         echo CC -o $*.o $<
 > 
 > (and an existing foo/bar.cc
 > 'make' ouputs 'CC -o foo/bar.o foo/bar.cc' while
 > 'make -j2' outputs 'CC -o bar.o foo/bar.cc', ie the target misses the directory part in parallel make
 > 
 The results will be even more surprising (at a glance) if you try
 this with ``make -r'' and ``make -r -j2''.  This is because you're
 misusing the inference rules in sys.mk and ${.PREFIX} (aka $*) and
 ${.IMPSRC} (aka $<) macros which are defined only for inference rules.
 The corrected makefile would look like this:
 
 : foo/bar.o: foo/bar.cc
 : 	@echo CC -o $@ $>
 
 or better yet:
 
 : foo/bar.o: foo/bar.cc
 : 	@echo CC -o ${.TARGET} ${.ALLSRC}
 
 which gives the same results in all four make(1) invocations.
 But please be aware that ${.ALLSRC} is dangerous because once
 you create a .depend file, there might be a dependency of the
 form ``bar.o: bar.h'' in it, and bar.h will become part of
 ${.ALLSRC}.  So the safe version would look like this:
 
 : foo/bar.o: foo/bar.cc
 : 	@echo CC -o ${.TARGET} foo/bar.cc
 
 If you need lot of such rules, you may start using the inference rule:
 
 : $ cat Makefile
 : .SUFFIXES: .cc .o
 : .cc.o:
 : 	@echo CC -o ${.TARGET} ${.IMPSRC}
 : $ make foo/bar.o
 : CC -o foo/bar.o foo/bar.cc
 : $ make -j2 foo/bar.o
 : CC -o foo/bar.o foo/bar.cc
 : $ make -r foo/bar.o
 : CC -o foo/bar.o foo/bar.cc
 : $ make -r -j2 foo/bar.o
 : CC -o foo/bar.o foo/bar.cc
 
 
 Cheers,
 -- 
 Ruslan Ermilov
 FreeBSD committer
 ru@FreeBSD.org