[U-Boot] [PATCH 1/3] compiler_gcc: do not redefine __gnu_attributes

[Jeroen Hofstee <jeroen@myspectrum.nl>]

Hello Masahiro,

On 18-09-14 04:13, Masahiro Yamada wrote:
> Jeroen,
>
>> commit fb8ffd7cfc68b3dc44e182356a207d784cb30b34 "compiler*.h:
>> sync include/linux/compiler*.h with Linux 3.16" undid the changes
>> of 7ea50d52849fe8ffa5b5b74c979b60b1045d6fc9 "compiler_gcc: do
>> not redefine __gnu_attributes". Add the checks back whether these
>> macro's are already defined (as it causes a lot of noise on e.g.
>> FreeBSD where these defines are already in cdefs.h)
>>
>> As the original patch this checkpatch warning is ignored:
>> "WARNING: Adding new packed members is to be done with care"
>
> Strange.
>
> Which source files include cdefs.h?
The host std* include this file, not a source file.

> For building u-boot images, sources should
> only include headers in the u-boot source tree.
> The standard system headers should not be used
> except only a few files such as <stdarg.h>.
>
> This is the same as Linux Kernel.

Yes, and stdarg.h includes cdefs.h. So each include of common.h
causes several warnings.

>
> On the contrary, host programs are allowed to use
> standard system headers such as <stdio.h>, <stdlib.h> etc,
> where <linux/compiler.h> should not be included.
>
>
> The root cause of warnings is _not_ that
> __packed and __weak are always defined in compiler-gcc.h.

This only works properly it u-boot for the target does not depend
on any host header at all, which as you mentioned is not the case.
Hence we shouldn't be surprised if they define something in their
namespace and hence checking if that is done is fine.

> I believe the real problem is there are some source files include
> both system headers and <linux/compiler.h> at the same time.
>

No it is a header issue only. The only alternative I can think of is a
custom version of stdarg etc and I don't really like that idea.

Regards,
Jeroen