Re: [Patch 04/18] include/linux/logfs.h

[Arnd Bergmann <arnd@arndb.de>]

On Wednesday 06 June 2007, David Woodhouse wrote:
> And if I had something like this (which is admittedly contrived, but
> hardware people _do_ do stupid things to us):
>    { uint32_t, uint8_t, uint16_t, uint8_t, uint32_t, uint32_t }
> 
> With the 'packed' attribute the compiler would assume arbitrary
> alignment of all the 32-bit integers. But in reality it's only necessary
> for the uint16_t in the middle. A 'nopadding' attribute would deal with
> that correctly.

I would argue that a newly invented 'nopadding' attribute should reject
such a structure as invalid, because it should not let members be
unaligned. Unfortunately, this also gets tricky if you consider

struct {
	uint32_t a;
	uint64_t b;
	uint32_t c;
};

which does have an unaligned member by default in i386, but not on
any modern platform.

	Arnd <><