Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!udel!princeton!newross!dynamic.Princeton.EDU!nr
From: nr@Princeton.EDU (Norman Ramsey)
Newsgroups: comp.lang.modula3
Subject: help wanted with Thread.Alert
Message-ID: <1991Apr4.015610.13835@newross.Princeton.EDU>
Date: 4 Apr 91 01:56:10 GMT
Sender: news@newross.Princeton.EDU (USENET News System)
Organization: Princeton University, Dept. of Computer Science
Lines: 53
Originator: nr@dynamic.Princeton.EDU

I don't understand why my thread isn't raising Thread.Alerted in the
following program:

  MODULE Alert EXPORTS Main;
  IMPORT Rd, Wr, Thread, Fmt;
  FROM Stdio IMPORT stdin, stdout;
  
  PROCEDURE Copy(cl:Thread.Closure):REFANY RAISES {} =
  VAR result := NEW(REF INTEGER);
  BEGIN
    result^ := 0;
    TRY
      LOOP
        WITH line = Rd.GetLine(stdin) DO
  	INC(result^);
          Wr.PutText(stdout,Fmt.F("line is `%s\'\n",line));
        END;
      END;
    EXCEPT Thread.Alerted => Wr.PutText(stdout,"Alert!\n");
    | Rd.EndOfFile => Wr.PutText(stdout,"EOT\n");
    END;
    RETURN result;
  END Copy;
  
  VAR t := Thread.Fork(NEW(Thread.Closure, apply := Copy));
  
  BEGIN
    Thread.Alert(t);
    Wr.PutText(stdout,"Thread has been alerted.\n");
    Wr.PutText(stdout,Fmt.F("Read %s lines\n",
                            Fmt.Int(NARROW(Thread.Join(t),REF INTEGER)^)));
  END Alert.
  
Here's some output:
nr@hart (44) % a.out
Thread has been alerted.
one
line is `one'
two
line is `two'
three
line is `three'
EOT
Read 3 lines


Can anybody help me understand this behavior?  I have a much larger,
more complicated program that's getting hung on exit because there's a
thread lingering around trying to read stdin and I can't successfully
alert the thread.
-- 
Norman Ramsey
nr@princeton.edu