RE: [PATCH] drivers: staging: lustre: lustre: include: add"__attribute__((packed))" for the related union

[David Laight]

From: Dan Carpenter
> On Sat, Feb 01, 2014 at 09:57:39PM +0800, Chen Gang wrote:
> > It seems, our kernel still stick to treate 'pack' region have effect
> > with both 'align' and 'sizeof'.
> 
> It's not about packed regions.  It's about unions.  It's saying the
> sizeof() a union is a multiple of 4 unless it's packed.
> 
> union foo {
> 	short x;
> 	short y;
> };
> 
> The author intended the sizeof(union foo) to be 2 but on metag arch then
> it is 4.

The same is probably be true of: struct foo { _u16 bar; };

Architectures that define such alignment rules are a right PITA.
You either need to get the size to 2 without using 'packed', or
just not define such structures.
It is worth seeing if adding aligned(2) will change the size - I'm
not sure.

	David



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