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From: angst%csilvax@hub.ucsb.edu (vaguely human)
Newsgroups: comp.lang.ada
Subject: PL/1 a dead language?
Message-ID: <637@hub.ucsb.edu>
Date: 25 May 88 09:40:49 GMT
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List-Id: <comp.lang.ada>

Ok, so this has nothing to do with PL/1.  Got you to look at least.

Anyone have any negative experiences with the TeleGen 2.15 (I think)
compiler for the Sun 3?  We are engaged in a fault tolerant software
experiment, and are using the TeleGen compiler.  Our programs have
many concurrent tasks, and it seems that the TeleGen compiler is way
faulty.  For one thing, it seems that guards (i.e. when statements)
on accept statements simply do not get evaluated sometimes.

I enclose a short sample program.

-------------------- START OF PROGRAM ---------------------

with text_io; use text_io;

procedure blah is

    task bogus is
	entry maybe;
    end bogus;

    task body bogus is
	x : integer := 1;

    begin
	loop
	    if x > 10 then
		put_line ("x>10");
	    end if;
	    select
		when (x > 10) =>
		    accept maybe do
			put_line ("we made it");
		    end;
		    exit;
	    or				-- XXX
		delay 1.0;
		x := x + 1;
		put_line ("can't accept yet");
	    end select;
	end loop;
    end bogus;

begin
    bogus.maybe;
end blah;

-------------------- END OF PROGRAM -----------------------

With the TeleGen compiler, the program prints "we made it" then exits.
This does not seem correct to me.  When I compile this with the Verdix
Ada compiler on our Vax, the program prints "==> DEADLOCK! <== No tasks
to run, no delays waiting."  If I change the "or" marked with "XXX" to
an "else," the programs works "as expected" for both compilers, i.e.
it prints "can't accept yet" 9 times, then prints "we made it" and exits.

Anyone have any ideas?  Please email unless you feel it would be of
interest to the group as a whole.  Many thanks in advance!

P.S. If you want to try the program on your compiler, I'd be interested
to know what happens.

	     "The stuff that undermines the best of me and you"

It was a pleasure |	        Dave Stein	      | on my back.  Just a
to meet you, you  |     angst%csilvax@hub.ucsb.edu    | pleasure to meet you,
slapped me right  |  ...ucbvax!ucsbcsl!csilvax!angst  | you got it almost exact.