Unless 2011 has change the default run-time library, 
When GNAT is installed the RTL is rts-native. Native uses the 
thread package of the underlying OS.

"FSU threads library", "pthreads library" (Solaris only), 
"Zero-Cost Exceptions" ("ZCX"), and "setjmp/longjmp" 
("SJLJ"), are optional if compiled, by using the "--RTS=" 
command line option.

Note: "FSU threads library" provide a completely accurate implementation 
of Annex D. Since "Glade" was replaced, not sure if GNAT, still provide 
a true implementation of Annex D.



In <nospam-6370B2.05223211092011@news.aioe.org>, "John B. Matthews" <nospam@nospam.invalid> writes:
>In article <j4hqvt$6pa$1@dont-email.me>, "J-P. Rosen" <rosen@adalog.fr> 
>wrote:
>
>> Le 10/09/2011 17:19, Simon Wright a écrit :
>> > It used to be that you could configure GNAT to use a tasking RTS that
>> > didn't use threads; tasks were scheduled entirely within the RTS. I
>> > think these may be called 'green threads'[1]. Of course, this meant that
>> > blocking on I/O would block the whole program, but for some purposes it
>> > might be ideal.
>> > 
>> No, it used the FSU threads
>
>FSU threads were used to implement Ada tasking in Tenon's MachTen and 
>CodeBuilder products for Mac OS 9.
>
><http://www.tenon.com/products/machten/>
>
>-- 
>John B. Matthews
>trashgod at gmail dot com
><http://sites.google.com/site/drjohnbmatthews>