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From: sbelmont700@gmail.com
Newsgroups: comp.lang.ada
Subject: OS support for ATC's
Date: Wed, 23 May 2012 17:18:56 -0700 (PDT)
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Date: 2012-05-23T17:18:56-07:00
List-Id: <comp.lang.ada>

The LRM 9.7.4 defines an "Asynchronous Transfer of Control" (otherwise know=
n as an abortable select statment), where one part can be preempted by the =
acceptance of an entry in the other.  GNAT, however, defines a compiler-spe=
cific "polling" pragma that is ostensibly required to support ATC's on "tar=
gets that cannot otherwise support it", and Windows is given as the example=
.

I suppose it's more a GNAT-specific question, but how does one know if ATC'=
s are supported on some arbitray target (DOS, Vxworks, brand-X linux, OS/2,=
 etc)?  The LRM makes no mention that they might not be supported, so it se=
ems odd to me that GNAT requires specific action to make it so, and moreso =
that they provide no particular guidance on when it's required and presumab=
ly would compile a program that would not work (i.e. if the polling pragma =
was not turned on for windows, I assume it would simply not abort when requ=
ired).

-sb