Re: [RFC] Splitting out kernel<=>userspace ABI headers

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

Sam Ravnborg wrote:
>  
> 
>>The kernel predates C99, sort of, and it would be a massive but valuable 
>> task to figure out where a type is really, for instance, 32 bits 
>>rather than "size of default int" in length, etc, and use POSIX types 
>>where they are correct. Fewer things to maintain, and would make it 
>>clear when something is 32 bits by default and when it really must be 32 
>>bits.
> 
> This has been discussed several times on lkml.
> Ask google...
> In short - the kernel provide its own namespace, and here __u32 etc is
> used. And starting to change that would be a noisy effort with no or
> limited gain neither for the kernel nor userspace.
> 

More specifically, replacing u32 with uint32_t as the kernel-internal 
type would be fine and arguably useful; in fact, a handful of drivers I 
believe already use it.

Replacing __u32 with uint32_t would be wrong, because it would require 
some user space headers that cannot include <stdint.h> to have to do so. 
  POSIX has *very* specific rules for namespace pollution, and most 
libcs have to care about that (klibc doesn't, but it's an exception, not 
the rule.)

	-hpa