Re: [RFC][PATCH] A generic boolean

["H. Peter Anvin" <hpa@zytor.com>]

Jes Sorensen wrote:
>>
>> And what will break if you make that switch?
> 
> If we are lucky, some binary only modules? :-)
> 
> But you're right, it may just have to be documented as one of those
> nasty issues to watch out for.
> 

What is really poisonous is structures which get padded when all the 
members are naturally aligned.  Unfortunately gcc produces really crap 
code with __attribute__((packed)) on some architectures, so just using 
that isn't a good solution.  On the other hand, non-AEABI ARM sometimes 
needs it!

For the lack of a __attribute__((nopad)) that would throw a warning or 
error on excessive padding, I fear that our best option is an __abi 
annotation which would enforce certain rules using sparse, and 
presumably provide __attribute__((packed)) on ARM:

- All padding must be explicit.
- All members must be naturally aligned.
- No unportable constructs, like non-int-sized bitfields.

	-hpa