Re: kernel header separation

[David Garfield]

Erik Andersen writes:
 > On Fri Sep 05, 2003 at 03:41:54PM +0100, Matthew Wilcox wrote:
 > > On Tue, Sep 02, 2003 at 07:49:09PM -0600, Erik Andersen wrote:
 > > > Header files intended for use by users should probably drop
 > > > linux/types.h just include <stdint.h>,,,  Then convert the 
 > > > types over to ISO C99 types.
 > > 
 > > stdint.h is a userspace header.  I suppose we could clone it for the
 > > kernel, but I don't see any need to.
 > > 
 > > > s/__u8/uint8_t/g
 > > > s/__u16/uint16_t/g
 > > > s/__u32/uint32_t/g
 > > > s/__u64/uint64_t/g
 > > 
 > > i think all these _t types are ugly ;-(
 > 
 > They may be ugly, but they are standardized and have very 
 > precise meanings defined by ISO C99, which is a very good
 > thing for code interoperability...
 > 
 >  -Erik

On the other hand, the ISO C99 definition is probably something like:
an integral type capable of storing the values 0 through 255
inclusive.  (ok, I don't have a copy of the new standard but I have
seriously examined the old one.)  I would not count on uint8_t
necessarily being unsigned on unusual hardware.  Linux on the other
hand probably means __u8 as an exactly eight bit unsigned integer
value.  While these may LOOK like identical statements, Linux is
[probably] making a significantly stronger statement.

I would say - keep the Linux types, and then document exactly what
Linux means by them somewhere.  In particular, if Linux were ported to
a 9/18/36 bit platform, what would the semantics of __u8 be?  (Ok,
maybe the documentation should say such a port is not considered to be
viable at this time.)

--David Garfield

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