Date: Mon, 23 Sep 2002 17:35:16 +0200 From: Roman Neuhauser <neuhauser@bellavista.cz> To: Bruce M Simpson <bms@spc.org>, freebsd-hackers@FreeBSD.ORG Subject: Re: two make questions Message-ID: <20020923153516.GC30361@freepuppy.bellavista.cz> In-Reply-To: <20020923150811.GI23343@spc.org> References: <20020923133431.GZ30361@freepuppy.bellavista.cz> <20020923095217.O332-100000@april.chuckr.org> <20020923143523.GA30361@freepuppy.bellavista.cz> <20020923150811.GI23343@spc.org>
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# bms@spc.org / 2002-09-23 16:08:11 +0100:
> On Mon, Sep 23, 2002 at 04:35:23PM +0200, Roman Neuhauser wrote:
> > thanks a lot for your reply. You're right: I'm viewing Makefiles
> > as sequential programs, which obviously (even to me) is not quite
> > true, but I'm having difficulty getting rid of this.
>
> Yeah, it takes a bit of getting used to. Make lets you define a dependency
> graph, and various transformations/instructions that can be applied to
> each node in that graph. In that respect it's more like a Caesar salad,
> the dependencies are the lettuce and the variables are croutons. Making it
> work is the dressing; you have to add it yourself ;-)
:)
> "Managing Projects with Make" from O'Reilly is a good introduction but it's
> a tad dated.
yeah, i'll be ordering it shortly.
> Also, make has a habit of being different from one platform to the
> next. I particularly like the BSD pmake, but Solaris make is different
> still, and GNU make is a law unto itself.
i know. i'm limiting myself to pmake atm, so other implementations
are out of the scope of my questions.
> > Now, saying "don't do it" is nice, but I'd like to know why. Why
> > doesn't this work? Also, what documentation (besides the source) is
> > there that covers variable scopes? See the second message for the
> > problem description.
>
> The scope of a Makefile macro (variable) seems to be limited to the current
> invocation,
? see below
> unless you explicitly export things as environment variables,
> or set them on a command line when re-invoking Make.
i'm not sure what to take of this. consider this makefile:
DESTDIR=
SOURCES= foo bar baz
TARGETS:= ${SOURCES:C;^;${DESTDIR}/;}
SRCFILE= ${.TARGET:C,^${DESTDIR}/,,}
.BEGIN:
@echo "\$${DESTDIR}: ${DESTDIR}"
@echo "\$${TARGETS}: ${TARGETS}"
all: ${TARGETS}
${TARGETS}: ${SRCFILE}
@echo "SRC: ${SRCFILE} -> TGT: ${.TARGET}"
.PHONY: all ${TARGETS}
roman@freepuppy ~/tmp 1133:0 > make all DESTDIR=/tmp/maketest
${DESTDIR}: /tmp/maketest
${TARGETS}: /foo /bar /baz
Graph cycles through /foo
Graph cycles through /bar
Graph cycles through /baz
`all' not remade because of errors.
roman@freepuppy ~/tmp 1133:0 >
in the invocation above, the commandline assignment overrode the
Makefile value of DESTDIR in the .BEGIN target, but not outside it
(or presumably any target), in the ${TARGETS} and ${SRCFILE} macros.
So: what exactly do you mean by "the current invocation"?
> Depending on what you want to do this can get quite complicated. Have
> a look at /usr/src/Makefile which actually reinvokes itself quite a
> bit (and includes things from Makefile.inc which may *also* do that!).
I've had more than a few looks in /usr/ports/Mk/bsd.port.mk, but
getting the "building block" principles from something that
complicated is not easy.
> Nik Clayton mentioned a tool to automatically diagram makefile dependency
> graphs by target at the last FreeBSD UKUG meeting, using graphviz, but I
> can't recall its name.
I'll google, thanks.
> > I can fix the behavior with conditional assignment to DESTDIR (?=)
> > in the Makefile, but still would like to understand what's causing
> > make to behave the way it does.
>
> If you're including any standard makefile templates you may wish to
> review those; as well as /etc/make.conf and /etc/defaults/make.conf.
nothing like that. my Makefiles break withoug the need for this
stuff. :)
> You probably also want to look at the MAKEOBJDIRPREFIX behaviour in
> the make(1) man page.
will do so.
thanks!
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