linux-kernel - Re: [PATCH] ASoC: core: Fix Sparse incompatible types warning

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Date:	Thu, 10 Apr 2014 04:01:50 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Mark Brown <broonie@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: core: Fix Sparse incompatible types warning

On Wed, Apr 09, 2014 at 10:28:59PM +0200, Lars-Peter Clausen wrote:

> I had a look at the sparse code and the problem is that it sets the
> default return type of sizeof according to the type of the host it
> was compiled on (either unsigned int or unsigned long). It can be
> overwritten by switches like -m32, but of course wont work when
> cross compiling. So if your host system is 64bit, but your target
> system is 32bit you'll get that warning.

Not that simple.  First of all, you *need* to tell sparse what target
to expect; size_t is the least of your troubles - sizeof(long) has
far more widespread impact.  If you don't get -m64 or -m32 in CFLAGS
(and on quite a few cross-builds you get it, simply because the target
is biarch and gcc itself needs to know what to generate), you need
to set it in CHECKFLAGS, along with other target-specific things.
Example:
arch/ia64/Makefile:21:CHECKFLAGS        += -m64 -D__ia64=1 -D__ia64__=1 -D_LP64 -D__LP64__

With the defaults being what they are (since commit 7aa79f "Adding default for
m64/m32 handle"), we probably need explicit -m32 in CHECKFLAGS for a bunch
of 32bit targets.  Defaults are iffy, BTW - it's not even "do as host does",
it's "64bit if the host is amd64, 32bit otherwise" ;-/

Again, CHECKFLAGS need to be set; that's normally done in arch/*/Makefile.

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