Re: [PATCH] Do not warn about char __attribute__((packed))

[Richard Guenther <rguenther at suse dot de>]

On Thu, 15 Dec 2005, Nathan Sidwell wrote:

> Richard Guenther wrote:
> > Recently the following warning was introduced, which triggers in
> > cases where it doesn't make any difference if its packed or not, like
> > 
> > /usr/src/linux/include/asm/mpspec_def.h:
> >    [...]
> > 74 struct mpc_config_bus
> > 75 {
> > 76        unsigned char mpc_type;
> > 77        unsigned char mpc_busid;
> > 78         unsigned char mpc_bustype[6] __attribute((packed));
> > 79 };
> > 
> > The following patch changes the logic to only warn if we try to
> > pack things that have type alignment smaller than BITS_PER_UNIT.
> 
> Are there such types?  Are there systems where the alignment of array of Foo
> is greater than plain Foo? (I.e. are there systems where the above attribute
> does something?)

I doubt it.  But 6.7.2.1/12 doesn't tell anything special about
array members, so it might be aligned differently and still be
standard conformant.

Richard.