[Buildroot] [PATCH] Adding Fluxbox window manager

Thomas Petazzoni thomas.petazzoni at free-electrons.com
Wed Aug 3 07:56:32 UTC 2011

Le Wed, 3 Aug 2011 09:46:16 +0200,
Thomas De Schampheleire <patrickdepinguin+buildroot at gmail.com> a écrit :

> >> +FLUXBOX_VERSION:=1.3.1
> >> +FLUXBOX_SOURCE:=fluxbox-$(FLUXBOX_VERSION).tar.bz2
> >> +FLUXBOX_SITE:=http://$(BR2_SOURCEFORGE_MIRROR).dl.sourceforge.net/sourceforge/fluxbox/
> >
> > Please use = instead of :=.
> Just curious: why do you recommend against := ?
> For example in the case of FLUXBOX_SOURCE, using := would avoid
> unnecessary expansions of $(FLUXBOX_VERSION), each time FLUXBOX_SOURCE
> is used.
> For FLUXBOX_SITE it depends on whether BR2_SOURCEFORGE_MIRROR is
> already defined or not, but I think it has, right?

Peter Korsgaard said:

:= is only a performance advantage if variables are expensive to expand
(use) and are used more than once - E.G. stuff involving $(shell) and
similar, like the UPPERCASE macro we had calling tr.

= has a number of advantages though. As it only gets expanded at the
last possible moment you don't have to take care about variable
ordering, E.G. when you use a variable like LIBGLIB2_HOST_BINARY on
another package, whereas with := you do. This can also be interesting
when the variable contains $(shell) or other functions, as you might
only want to execute them if/when they are needed, and not right away
when the Makefiles are parsed.

I would prefer to use = by default, and only use := where it matters for
correctness or performance.


Subject: Re: [Buildroot] [PATCH 07/28] barebox: use = instead of := and re-indent
Date: Tue, 05 Jul 2011 23:04:58 +0200
Message-ID: <87sjqkv3ph.fsf at macbook.be.48ers.dk>


Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.

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