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

[Segher Boessenkool <segher@kernel.crashing.org>]

>>> It would be better if GCC had a 'nopadding' attribute which gave us
>>> what we need without the _extra_ implications about alignment.
>>
>> That's impossible; removing the padding from a struct
>> _will_ make accesses to its members unaligned (think
>> about arrays of that struct).
>
> It _might_ make accesses to _some_ of its members unaligned.

It _will_ make accesses to _at least one_ of the members
unaligned, in the second array element.

> That's why I said 'without the __EXTRA__ implications about alignment'.
>
> Obviously the lack of padding has its own implications, but we don't
> necessarily need to assume that the struct may be at arbitrary
> locations.

The compiler does though, if it can't prove otherwise.

What would "nopadding" buy us, anyway?


Segher