linux-kernel - Re: [PATCH 0/5] x86/pci: patches for tip/x86/unify-pci

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Message-ID: <20080711102844.GB22725@uranus.ravnborg.org>
Date:	Fri, 11 Jul 2008 12:28:44 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Robert Richter <robert.richter@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/5] x86/pci: patches for tip/x86/unify-pci

> > 
> > obj-y is empty when you enter the Makefile.
> > So if you start out with ':=' or '+=' is no difference.
> 
> i guess it's safer to use +=, because it's ordering invariant.
> 
> We should use := only if we absolutely want to override the current 
> rules.

In the past I was carefully to use ':=' for the first assignmnet so the
variable was a " simply expanded variables" variable.
But as I have added a 'obj-y := ' in kbuild we should
be safe.

" simply expanded variables" is some special make stuff.

A typical:

FOO = bar

is a "recursively expanded variable".
Here the assingment is evaluated on each usage.

	Sam
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