[Tux3] [PATCH 03/10] Fix ileaf aligment

[Daniel Phillips]

On Friday 17 October 2008 03:45, OGAWA Hirofumi wrote:
> Daniel Phillips <phillips at phunq.net> writes:
> >> >> Good catch.  A better way to fix this is using gcc attribute packed,
> >> >> which is done by the Tux3 macro PACKED:
> >> >
> >> > But, I think the result of it is aliment fault on some archs.
> >> 
> >> if we accessed ->ibase. Or we should use get_unaligned()?
> >
> > I think we do want to pad it just as you have done.  We do need to get
> > unaligned in other code, the inode attributes specifically, and make
> > sure that always works.  We also do an endian conversion every time we
> > do this, so it is always going to be wrapped in a macro.  But I am not
> > sure that the endian macros can handle unaligned accesses on all
> > architectures.
> 
> I see. BTW, Linux has macros for it - get_unaligned_be*/_le*.

According to this, attribute ((packed)) is supposed to imply unaligned:

     http://www.ohse.de/uwe/articles/gcc-attributes.html#var-packed
     "The `packed' attribute specifies that a variable or structure field
     should have the smallest possible alignment--one byte for a
     variable, and one bit for a field, unless you specify a larger
     value with the `aligned' attribute."

Please correct me if I'm wrong.

Daniel

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