Re: [PATCH linux-next] net: batman-adv: use "__packed __aligned(2)"for each structure instead of "__packed(2)" region

From: James Hogan
Date: Mon Jan 20 2014 - 06:29:01 EST

Hi Antonio,

On 19/01/14 09:30, Antonio Quartulli wrote:
> On 19/01/14 02:10, James Hogan wrote:
>> It appears that the following gcc patch adds support for #pragma pack:
>> I gave it a quick spin on metag gcc (which is unfortunately stuck on an old
>> version) and it seems to fix my simple test case so that #pragma pack(2)
>> becomes equivalent to __packed __aligned(2) (for sizeof and __alignof__).
> Then I personally think that it is better to fix metag gcc instead of
> changing the kernel.

Indeed it makes sense to patch metag gcc to be safe in the presence of
unportable code like this.

> Actually there are many different spots where "#pragma pack" is used.
> batman-adv is just the only one having compile time checks for structure
> sizes.

Well the only vaguely interesting one I can find outside of drivers is
in fs/udf, and even that seems specific to CD-ROMs and DVDs.

If you care about portability then Chen's patch looks reasonable to me.


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