svn commit: r224721 - head/sys/sys

[Alexander Best]

On Mon Aug 15 11, Alexander Best wrote:
> On Mon Aug 15 11, Bruce Evans wrote:
> > On Wed, 10 Aug 2011, Alexander Best wrote:
> > 
> > >On Wed Aug 10 11, Bruce Evans wrote:
> > >>On Wed, 10 Aug 2011, Alexander Best wrote:
> > >>>any reason {TIMEVAL,TIMESPEC}_TO_{TIMESPEC,TIMEVAL}()s code is being
> > >>>executed
> > >>>in a
> > >>>
> > >>>do { ... } while (0)
> > >>>
> > >>>conditional loop?
> > >>
> > >>Just the usual syntactical trick for making large macros that look
> > >>like function calls almost usable like function calls.  Without the
> > >...
> > >thanks a lot for the in depth information. :) any reason, back in the 
> > >days, it
> > >was decided that the functionality of converting a timespec to a timeval 
> > >and
> > >vice versa should be implemented as a macro and not a function?
> > 
> > Macros avoid some namespace pollution problems, and all the old kernel
> > timeval manipulation interfaces are either extern functions or macros,
> > partly because inline functions didn't exist when these interfaces were
> > designed.  But the TIME* macros still have gratuitously different styles:
> > 1) they are spelled in upper case (which is "correct" since they are unsafe
> >    macros, but this is not done for the other timeval macros which are 
> >    almost
> >    all unsafe)
> > 2) FreeBSD moved their definitions from <sys/time.h> (where 4.4BSD-Lite
> >    put them) to <sys/timespec.h>.  This is not incorrect (since <sys/time.h>
> >    is an old header that should only declare timeval interfaces (POSIX
> >    put timespec interfaces in <time.h>).  However, the move became out of
> >    date before it was done (in 2001) because <sys/time.h> had already
> >    grown several other timespec interfaces which were not moved.  But these
> >    were kernel-only, so they didn't cause namespace problems.  Now
> >    <sys/time.h> has grown several more user timespec interfaces.
> 
> thanks for the explanation. :)

sorry. this was supposed to go to bde@ alone and not the lists.

> 
> > 
> > Bruce