[asterisk-dev] [asterisk-commits] tilghman: trunk r232164 - in /trunk: ./ include/asterisk/ main/

[Tilghman Lesher]

On Wednesday 02 December 2009 06:49:29 Kevin P. Fleming wrote:
> SVN commits to the Asterisk project wrote:
> > Author: tilghman
> > Date: Tue Dec  1 21:26:16 2009
> > New Revision: 232164
> >
> > URL: http://svnview.digium.com/svn/asterisk?view=rev&rev=232164
> > Log:
> > So apparently, some platforms don't have ffsll(3).
> > The manpage lies; it says that the function is in POSIX, but that's only
> > for ffs(3), not ffsll(3).
>
> Since we already require gcc for compilation, and gcc provides
> __builtin_ffsll(), this should not be necessary. In fact, Russell has
> already changed the code to use __builtin_ffsll() anyway.

The GCC manual states that if no optimizations are done for the builtin
function, then the compiler will emit a call to the library function, instead.
Given that development typically runs with the DONT_OPTIMIZE flag set,
it would seem to suggest that for platforms which do not have this function,
we would be making it impossible to debug or develop code there, without
supplying this function.

I'm open to being proved wrong, but it looks like we need to tread carefully
to use any of the __builtin_ variety of functions in our code to get around
cross-platform issues.  GCC states their use only makes sense for
optimization.

http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other-Builtins

-- 
Tilghman Lesher
Digium, Inc. | Senior Software Developer
twitter: Corydon76 | IRC: Corydon76-dig (Freenode)
Check us out at: www.digium.com & www.asterisk.org