Re: ADA-9x done? Any good PC compilers?

Re: ADA-9x done? Any good PC compilers?

[Robert Dewar]

You asked for Ada on a PC platform, so it is worth pointing out that the
OS/2 version of GNAT on the PC does support tasking.

P.S. the delay bug is fixed in the latest development version people will
be glad to hear!

Actually it was not technically a bug, since compilers are allowed to
take longer than the minimum for a delay, if you had waited 25,000 years,
the delay would have expired :-) :-)

Re: ADA-9x done? Any good PC compilers?

[Howard.Gilbert]

In <3f49k3$kfp@gnat.cs.nyu.edu>, dewar@cs.nyu.edu (Robert Dewar) writes:
>
>Actually it was not technically a bug, since compilers are allowed to
>take longer than the minimum for a delay, if you had waited 25,000 years,
>the delay would have expired :-) :-)

Now you are beginning to sound like Microsoft.

Re: ADA-9x done? Any good PC compilers?

[Robert Dewar]

I was talking about when a delay expires, this has nothing to do with the
required preemption by a higher priority task!
(responding to Eachus' note on my note about infinite delays)

Re: ADA-9x done? Any good PC compilers?

[Robert I. Eachus]

In article <3fk7j7$ld5@gnat.cs.nyu.edu> dewar@cs.nyu.edu (Robert Dewar) writes:

 > I was talking about when a delay expires, this has nothing to do with the
 > required preemption by a higher priority task!
 > (responding to Eachus' note on my note about infinite delays)

    RM83 9.6(1): The execution of a delay statement evaluates the
simple expression, and suspends further execution...for at least the
duration specified by the resulting value.

    RM83 9.8(4): If two tasks with different priorities are both
eligible for execution...then it cannot be the case that the task with
the lower priority is executing while the task with the higher
priority is not.

    The first creates a requirement that the delay must be at least
that specified in the expression, the second paragraph adds a
requirement which, on a single processor system, simplifies to: "The
highest priority eligible task must be executing, in case of ties, the
selection among the tied set is implemetation dependent."  Paragraph
9.6(1) does not conflict with or supercede 9.8(4).  They work
together.  Paragraph 9.6(1) declares certain tasks ineligible until
the delay expires, 9.8(4) specifies requirements with respect to
eligible tasks.

    I think you (Robert) perfectly well understand that the only
freedom granted by 9.6 with respect to 9.8 is that the clock for
interrupts need not be maintained to DURATION'SMALL resolution. The
resolution is found instead in SYSTEM.TICK.  If you want to validate a
system where SYSTEM.TICK = DURATION'LAST, fine.  But that still won't
allow infinite prolongation of delays.

--

					Robert I. Eachus

with Standard_Disclaimer;
use  Standard_Disclaimer;
function Message (Text: in Clever_Ideas) return Better_Ideas is...

Re: ADA-9x done? Any good PC compilers?

[Robert Dewar]

Robert Eachus is wrong in thinking System.Tick has anything to do with
delays in Ada 83 (I guess he missed the ARG meeting where we discussed
this :-)