Which header file?

Which header file?

[Amit Kumar]

Hi,
In linux/include/linux/atomic.h, there are two files included asm/atomic.h
and asm/barrier.h. Both files are present in linux/include/asm-generic and
linux/arch/arm/include/asm. If I build like,
CROSS_COMPILE=arm-linux-gnueabi- ARCH=arm make zImage dtbs
then which file is being used.

A kernel newbie,
Amit Kumar
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Which header file?

[Valdis.Kletnieks at vt.edu]

On Wed, 16 Nov 2016 21:01:19 +0000, Amit Kumar said:

> In linux/include/linux/atomic.h, there are two files included asm/atomic.h
> and asm/barrier.h. Both files are present in linux/include/asm-generic and
> linux/arch/arm/include/asm. If I build like,
> CROSS_COMPILE=arm-linux-gnueabi- ARCH=arm make zImage dtbs
> then which file is being used.

Hint 1: Check for symlinks.
Hint 2: Compile with  'make V=1' which will show the complete gcc command line,
so you can see the order of -I parameters.
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Which header file?

[Amit Kumar]

On Thu, Nov 17, 2016 at 5:00 AM <Valdis.Kletnieks@vt.edu> wrote:

> On Wed, 16 Nov 2016 21:01:19 +0000, Amit Kumar said:
>
> > In linux/include/linux/atomic.h, there are two files included
> asm/atomic.h
> > and asm/barrier.h. Both files are present in linux/include/asm-generic
> and
> > linux/arch/arm/include/asm. If I build like,
> > CROSS_COMPILE=arm-linux-gnueabi- ARCH=arm make zImage dtbs
> > then which file is being used.
>
> Hint 1: Check for symlinks.
> Hint 2: Compile with  'make V=1' which will show the complete gcc command
> line,
>
Thank you for your hints.
I have used omap2plus_defconfig. After issuing command,
 CROSS_COMPILE=arm-linux-gnueabi- ARCH=arm make zImage dtbs V=1 | tee
mybuild.log
I have got something like this,
...
-nostdinc -isystem /usr/lib/gcc-cross/arm-linux-gnueabi/5/include
-I./arch/arm/include -I./arch/arm/include/generated/uapi
-I./arch/arm/include/generated  -I./include -I./arch/arm/include/uapi
-I./include/uapi -I./include/generated/uapi -include
./include/linux/kconfig.h
...
First all -I is searched sequentially then -isystem dir is searched.
One additional thing I found that every file includes
./include/linux/kconfig.h which in turn includes generated/kconfig.h, which
I think is generated on the basis of .config, to check features enabled.

so you can see the order of -I parameters.
>
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