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Date:      Mon, 29 Nov 1999 10:51:25 +0100
From:      "Koster, K.J." <K.J.Koster@research.kpn.com>
To:        'FreeBSD Java mailing list' <freebsd-java@freebsd.org>
Subject:   Followup: appletvierer dies reproducably
Message-ID:  <59063B5B4D98D311BC0D0001FA7E45220FD060@l04.research.kpn.com>
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Dear FreeBSD Java,

As promised I've sat down and made an attempt to isolate the
crashing appletviewer bug. It seems to be related to memory
management problems. Quite ironic that a java application
dies on memory management, but that's a programmer's life
for you.

I reduced the applet to the merest splinter of what I had
previously. I tested this on FreeBSD 3.3 stable, with the
1999-11-9 build of JDK 1.1.8. It dies quite reliably now.
As a side note, it dies in the same way on a Sun Sparc, so I
guess solving this problem is not really a FreeBSD java port
issue. However, because of the more strict memory management
that FreeBSD does, I believe that FreeBSD developers have an
edge here.

Create the four files that I quoted below. Run "make all",
followed by "make client". An applet will start with two
text fields. Don't touch the text fields, but click on the
[Applet] meny item and select [Reload]. Repeat reloading the
applet.  On my system it dies after between two to five
reloads.

As you reload the applet, you may see malloc(3) complain
about chunks being freed, or pages and chunks being moved.
The JDK and FreeBSD clearly disagree on what proper memory
management is:

    LikeEver% make client
    /usr/local/jdk1.1.8/bin/appletviewer GameClient.html
    java_X in free(): warning: chunk is already free.
    java_X in free(): warning: chunk is already free.

The same behaviour I've observed in the GraphicsTest applet
in the JDK demos, although it only reports chunks to be
already free, and does not crash:

    LikeEver% cd /usr/local/jdk1.1.8/demo/GraphicsTest 
    LikeEver% appletviewer example1.html 
    java_X in free(): warning: chunk is already free.
    java_X in free(): warning: chunk is already free.
    java_X in free(): warning: chunk is already free.

Any idea what I'm doing wrong?

Kees Jan

==== - GameClient.html - ====
<html>
<body>
<p><applet code="GameClient.class" width=800 height=600>
</applet></p>
</body>
</html>


==== - GameClient.java - ====
import java.applet.Applet;

public class GameClient extends Applet
{
  public void init()
  {
    LoginPanel loginPanel = new LoginPanel();
    add(loginPanel);
  }
}


==== - LoginPanel.java - ====
import java.awt.Panel;
import java.awt.TextField;

public class LoginPanel extends Panel
{
  public LoginPanel()
  {
    TextField userBox = new TextField(25);
    add(userBox);

    TextField passwordBox = new TextField(25);
    passwordBox.setEchoChar('*');
    add(passwordBox);
  }
}


==== - Makefile - ====
JAVA_HOME=/usr/local/jdk1.1.8

CLASSPATH=$(JAVA_HOME)/lib/classes.zip

JAVA   = $(JAVA_HOME)/bin/java
JAVAC  = $(JAVA_HOME)/bin/javac
JAR    = $(JAVA_HOME)/bin/jar
RMIC   = $(JAVA_HOME)/bin/rmic
APPLET = $(JAVA_HOME)/bin/appletviewer

all:
	rm -rf *.class
	$(JAVAC) -classpath $(CLASSPATH) -d . *.java

client: GameClient.html
	$(APPLET) GameClient.html


===




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