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Re: substitution vs expansion in

From: Ralf Wildenhues
Subject: Re: substitution vs expansion in
Date: Tue, 4 Mar 2008 22:57:58 +0100
User-agent: Mutt/1.5.17+20080114 (2008-01-14)

Hi John,

* John Calcote wrote on Tue, Mar 04, 2008 at 10:38:50PM CET:
> Newbie question here: Is it better to do this in a
>    install-exec-hook:
>            $(mkdir_p) $(DESTDIR)@syslogdir@
> or this:
>    install-exec-hook:
>           $(mkdir_p) $(DESTDIR)$(syslogdir)
> assuming, of course, that I called AC_SUBST(syslogdir) in
> The first will expand to $(prefix)/..., so you'd have the option of
> changing the resulting directory by passing prefix= on the make
> command line. The second will allow you to change the resulting
> directory with either prefix= or syslogdir= on the make command line.
> I guess you'd get a bit more flexibility by using the second option
> because you could change the syslogdir without changing the prefix.
> But, is there a conventional, or more correct approach?

Nice question.  You already deliver the answer, including full rationale
and all: the second form is preferable because it allows more override.

In general, there is one other bit of difference between @foo@ and
$(foo) in that automake may not be able to look into the former.
But for this case that makes little difference.


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