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<p>Hey Martin,<br>
<br>
thank you for looking into this. The initial StackOverflow is a
result of me forcing to reproduce the bounds
IndexOutOfBoundsException. The StackOverflow can be ignored, it
was merely the best method I found to transition the scene graph
into a state where the IndexOutOfBoundsExceptions are thrown. The
OOBs are not thrown in every run though, it sometimes takes a few
tries. In our production application, the same
IndexOutOfBoundsExceptions also occur randomly without a previous
exception. You can probably also reproduce the
IndexOutOfBoundsExceptions without the StackOverflow, but
reproducing it was very fragile, so I didn't look into it more.<br>
<br>
I don't think it has necessarily something to do with the alert
bounds as the IndexOutOfBoundsException is also thrown if you
don't show an alert at all. The constant
IndexOutOfBoundsExceptions in combination with the alert
showAndWait was how our application entered the original crashing
state. So the reproducer is more like a two-in-one.<br>
<br>
Best<br>
Christopher Schnick<br>
</p>
<div class="moz-cite-prefix">On 26/03/2025 18:33, Martin Fox wrote:<br>
</div>
<blockquote type="cite"
cite="mid:9560C9BE-BC2F-4F0D-B914-425969699179@gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
Yes, thank you Christopher for providing a reproducible test case!
<div><br>
</div>
<div>I was able to trigger the problem on my Mac on the first try.
Since I’m using a modified version of JavaFX the system didn’t
crash but instead hit a Java stack overflow error and produced a
very long stack trace.</div>
<div><br>
</div>
<div>At least on the Mac the problem seems to be that you’re
trying to pop an Alert containing a long stack trace. While
trying to adjust the Alert’s bounds JavaFX is throwing another
exception but I’m not sure why. I’ll continue to look into it.</div>
<div><br>
</div>
<div>Thanks again,</div>
<div>Martin</div>
<div>
<div>
<div><br>
<blockquote type="cite">
<div>On Mar 25, 2025, at 12:16 PM, Andy Goryachev
<a class="moz-txt-link-rfc2396E" href="mailto:andy.goryachev@oracle.com"><andy.goryachev@oracle.com></a> wrote:</div>
<br class="Apple-interchange-newline">
<div>
<meta charset="UTF-8">
<div class="WordSection1"
style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Optima-Regular; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;">
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">Thank
you, Christopher, for clarification!<o:p></o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"><o:p> </o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">Personally,
I would consider this to be a problem with the
application design: the code should limit the
number of alerts shown to the user. Do you really
want the user to click through hundreds of alerts?<o:p></o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"><o:p> </o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">Nevertheless,
you are right about the need for the platform to
gracefully handle the case of too many nested
event loops - by throwing an exception with a
meaningful message, as Martin proposed in<span
class="Apple-converted-space"> </span><a
href="https://github.com/openjdk/jfx/pull/1741"
style="color: blue; text-decoration: underline;"
moz-do-not-send="true"
class="moz-txt-link-freetext">https://github.com/openjdk/jfx/pull/1741</a><o:p></o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"><o:p> </o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">Cheers,<o:p></o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">-andy<o:p></o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"><o:p> </o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"><o:p> </o:p></span></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"><o:p> </o:p></span></div>
<div id="mail-editor-reference-message-container">
<div>
<div>
<div
style="border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) currentcolor currentcolor; border-image: none; padding: 3pt 0in 0in;">
<p class="MsoNormal"
style="margin: 0in 0in 12pt; font-size: 10pt; font-family: Aptos, sans-serif;"><b><span
style="font-size: 12pt;">From:<span
class="Apple-converted-space"> </span></span></b><span
style="font-size: 12pt;">Christopher
Schnick <a class="moz-txt-link-rfc2396E" href="mailto:crschnick@xpipe.io"><crschnick@xpipe.io></a><br>
<b>Date:<span
class="Apple-converted-space"> </span></b>Tuesday,
March 25, 2025 at 11:52<br>
<b>To:<span class="Apple-converted-space"> </span></b>Andy
Goryachev
<a class="moz-txt-link-rfc2396E" href="mailto:andy.goryachev@oracle.com"><andy.goryachev@oracle.com></a><br>
<b>Cc:<span class="Apple-converted-space"> </span></b>OpenJFX
<a class="moz-txt-link-rfc2396E" href="mailto:openjfx-dev@openjdk.org"><openjfx-dev@openjdk.org></a><br>
<b>Subject:<span
class="Apple-converted-space"> </span></b>Re:
[External] : Re: JVM crashes on macOS when
entering too many nested event loops<o:p></o:p></span></p>
</div>
<p>Hey Andy,<br>
<br>
so I think I was able to reproduce this issue
for our application.<br>
<br>
There are two main factors how this can
happen:<br>
- We use an alert-based error reporter,
meaning that we have a default uncaught
exception handler set for all threads which
will showAndWait an Alert with the exception
message<br>
- As I reported yesterday with<span
class="Apple-converted-space"> </span><a
href="https://mail.openjdk.org/pipermail/openjfx-dev/2025-March/052963.html"
style="color: blue; text-decoration: underline;" moz-do-not-send="true"
class="moz-txt-link-freetext">https://mail.openjdk.org/pipermail/openjfx-dev/2025-March/052963.html</a>,
there are some rare exceptions that can occur
in a normal event loop without interference of
the application, probably because of a small
bug in the bounds calculation code<br>
<br>
If you combine these two factors, you will end
up with an infinite loop of the showAndWait
entering a nested event loop, the event loop
throwing an internal exception, and the
uncaught exception handler starting the same
loop with another alert. I don't think this is
a bad implementation from our side, the only
thing that we can improve is to maybe check
how deep the uncaught exception loop is in to
prevent this from occurring indefinitely. But
I would argue this can happen to any
application. Here is a sample code, based on
the reproducer from the OutOfBounds report
from yesterday:<o:p></o:p></p>
<div>
<pre
style="margin: 0in; font-size: 8pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">javafx.application.Application;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">javafx.application.Platform;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">javafx.scene.Scene;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">javafx.scene.control.Alert;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">javafx.scene.control.Button;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">javafx.scene.layout.Region;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">javafx.scene.layout.StackPane;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">javafx.scene.layout.VBox;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">javafx.stage.Stage;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"><o:p> </o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">java.io.IOException;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">import </span><span
style="color: rgb(188, 190, 196);">java.util.Arrays;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"><o:p> </o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(207, 142, 109);">public class </span><span
style="color: rgb(188, 190, 196);">ParentBoundsBug </span><span
style="color: rgb(207, 142, 109);">extends </span><span
style="color: rgb(188, 190, 196);">Application {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"><o:p> </o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(179, 174, 96);">@Override<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(179, 174, 96);"> </span><span
style="color: rgb(207, 142, 109);">public void </span><span
style="color: rgb(86, 168, 245);">start</span><span
style="color: rgb(188, 190, 196);">(Stage stage) </span><span
style="color: rgb(207, 142, 109);">throws </span><span
style="color: rgb(188, 190, 196);">IOException {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> Thread.<i>setDefaultUncaughtExceptionHandler</i>((thread, throwable) -> {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> throwable.printStackTrace();<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"><o:p> </o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(207, 142, 109);">if </span><span
style="color: rgb(188, 190, 196);">(Platform.<i>isFxApplicationThread</i>()) {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(207, 142, 109);">var </span><span
style="color: rgb(188, 190, 196);">alert = </span><span
style="color: rgb(207, 142, 109);">new </span><span
style="color: rgb(188, 190, 196);">Alert(Alert.AlertType.</span><i><span
style="color: rgb(199, 125, 187);">ERROR</span></i><span
style="color: rgb(188, 190, 196);">);<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> alert.setHeaderText(throwable.getMessage());<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> alert.setContentText(Arrays.<i>toString</i>(throwable.getStackTrace()));<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> alert.showAndWait();<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> } </span><span
style="color: rgb(207, 142, 109);">else </span><span
style="color: rgb(188, 190, 196);">{<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(122, 126, 133);">// Do some other error handling for non-platform threads<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(122, 126, 133);"> // Probably just show the alert with a runLater()<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(122, 126, 133);"><o:p> </o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(122, 126, 133);"> // For this example, there are no exceptions outside the platform thread<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(122, 126, 133);"> </span><span
style="color: rgb(188, 190, 196);">}<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> });<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"><o:p> </o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(122, 126, 133);">// Run delayed as Application::reportException will only be called for exceptions<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(122, 126, 133);"> // after the application has started<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(122, 126, 133);"> </span><span
style="color: rgb(188, 190, 196);">Platform.<i>runLater</i>(() -> {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> Scene scene = </span><span
style="color: rgb(207, 142, 109);">new </span><span
style="color: rgb(188, 190, 196);">Scene(createContent(), </span><span
style="color: rgb(42, 172, 184);">640</span><span
style="color: rgb(188, 190, 196);">, </span><span
style="color: rgb(42, 172, 184);">480</span><span
style="color: rgb(188, 190, 196);">);<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(199, 125, 187);">stage</span><span
style="color: rgb(188, 190, 196);">.setScene(scene);<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(199, 125, 187);">stage</span><span
style="color: rgb(188, 190, 196);">.show();<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(199, 125, 187);">stage</span><span
style="color: rgb(188, 190, 196);">.centerOnScreen();<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> });<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> }<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"><o:p> </o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(207, 142, 109);">private </span><span
style="color: rgb(188, 190, 196);">Region </span><span
style="color: rgb(86, 168, 245);">createContent</span><span
style="color: rgb(188, 190, 196);">() {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(207, 142, 109);">var </span><span
style="color: rgb(188, 190, 196);">b1 = </span><span
style="color: rgb(207, 142, 109);">new </span><span
style="color: rgb(188, 190, 196);">Button(</span><span
style="color: rgb(106, 171, 115);">"Click me!"</span><span
style="color: rgb(188, 190, 196);">);<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(207, 142, 109);">var </span><span
style="color: rgb(188, 190, 196);">b2 = </span><span
style="color: rgb(207, 142, 109);">new </span><span
style="color: rgb(188, 190, 196);">Button(</span><span
style="color: rgb(106, 171, 115);">"Click me!"</span><span
style="color: rgb(188, 190, 196);">);<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(207, 142, 109);">var </span><span
style="color: rgb(188, 190, 196);">vbox = </span><span
style="color: rgb(207, 142, 109);">new </span><span
style="color: rgb(188, 190, 196);">VBox(b1, b2);<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> b1.boundsInParentProperty().addListener((observable, oldValue, newValue) -> {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(199, 125, 187);">vbox</span><span
style="color: rgb(188, 190, 196);">.setVisible(!</span><span
style="color: rgb(199, 125, 187);">vbox</span><span
style="color: rgb(188, 190, 196);">.isVisible());<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> });<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> b2.boundsInParentProperty().addListener((observable, oldValue, newValue) -> {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(199, 125, 187);">vbox</span><span
style="color: rgb(188, 190, 196);">.setVisible(!</span><span
style="color: rgb(199, 125, 187);">vbox</span><span
style="color: rgb(188, 190, 196);">.isVisible());<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> });<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> vbox.boundsInParentProperty().addListener((observable, oldValue, newValue) -> {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(199, 125, 187);">vbox</span><span
style="color: rgb(188, 190, 196);">.setVisible(!</span><span
style="color: rgb(199, 125, 187);">vbox</span><span
style="color: rgb(188, 190, 196);">.isVisible());<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> });<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"><o:p> </o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(207, 142, 109);">var </span><span
style="color: rgb(188, 190, 196);">stack = </span><span
style="color: rgb(207, 142, 109);">new </span><span
style="color: rgb(188, 190, 196);">StackPane(vbox, </span><span
style="color: rgb(207, 142, 109);">new </span><span
style="color: rgb(188, 190, 196);">StackPane());<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> stack.boundsInParentProperty().addListener((observable, oldValue, newValue) -> {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(199, 125, 187);">vbox</span><span
style="color: rgb(188, 190, 196);">.setVisible(!</span><span
style="color: rgb(199, 125, 187);">vbox</span><span
style="color: rgb(188, 190, 196);">.isVisible());<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> });<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(207, 142, 109);">return </span><span
style="color: rgb(188, 190, 196);">stack;<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> }<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"><o:p> </o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> </span><span
style="color: rgb(207, 142, 109);">public static void </span><span
style="color: rgb(86, 168, 245);">main</span><span
style="color: rgb(188, 190, 196);">(String[] args) {<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> <i>launch</i>();<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);"> }<o:p></o:p></span></pre>
<pre
style="margin: 0in; font-size: 10pt; font-family: "Courier New"; background: rgb(30, 31, 34);"><span
style="color: rgb(188, 190, 196);">}<o:p></o:p></span></pre>
</div>
<p><br>
If the same OutOfBounds exception from the
reported I linked happens in the bounds
calculation, which happens approximately 1/5
runs for me, this application will enter new
event loops until it crashes. If the
OutOfBounds doesn't trigger, it will just
throw a StackOverflow but won't continue the
infinite loop of nested event loops. So for
the reproducer it is important to try a few
times until you get the described OutOfBounds.<o:p></o:p></p>
<p>I attached the stacktrace of how this fails.
The initial StackOverflow causes infinitely
many following exceptions in the nested event
loop.<o:p></o:p></p>
<p>Best<br>
Christopher Schnick<o:p></o:p></p>
<div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 12pt;">On 25/03/2025
18:28, Andy Goryachev wrote:<o:p></o:p></span></div>
</div>
<blockquote
style="margin-top: 5pt; margin-bottom: 5pt;">
<div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">Dear
Christopher:</span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">Were
you able to root cause why your
application enters that many nested
event loops?</span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">I
believe a well-behaved application
should never experience that, unless
there is some design flaw or a bug.</span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">-andy</span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
id="mail-editor-reference-message-container">
<div>
<div>
<div
style="border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) currentcolor currentcolor; border-image: none; padding: 3pt 0in 0in;">
<p class="MsoNormal"
style="margin: 0in 0in 12pt; font-size: 10pt; font-family: Aptos, sans-serif;"><b><span
style="font-size: 12pt;">From:<span
class="Apple-converted-space"> </span></span></b><span
style="font-size: 12pt;">Christopher
Schnick<span
class="Apple-converted-space"> </span><a
href="mailto:crschnick@xpipe.io"
style="color: blue; text-decoration: underline;" moz-do-not-send="true"><crschnick@xpipe.io></a><br>
<b>Date:<span
class="Apple-converted-space"> </span></b>Monday, March 10, 2025 at
19:45<br>
<b>To:<span
class="Apple-converted-space"> </span></b>Andy Goryachev<span
class="Apple-converted-space"> </span><a
href="mailto:andy.goryachev@oracle.com"
style="color: blue; text-decoration: underline;" moz-do-not-send="true"><andy.goryachev@oracle.com></a><br>
<b>Subject:<span
class="Apple-converted-space"> </span></b>[External] : Re: JVM crashes
on macOS when entering too many
nested event loops</span><o:p></o:p></p>
</div>
<p>Our code and some libraries do
enter some nested event loops at a
few places when it makes sense, but
we didn't do anything to explicitly
provoke this, this occurred
naturally in our application. So it
would be nice if JavaFX could
somehow guard against this,
especially since crashing the JVM is
probably the worst thing that can
happen.<br>
<br>
I looked at the documentation, but
it seems like the public API at
Platform::enterNestedEventLoop does
not mention this.<br>
From my understanding, the method
Platform::canStartNestedEventLoop is
potentially the right method to
indicate to the caller that the
limit is close by returning false.<br>
And even if something like an
exception is thrown when a nested
event loop is started while it is
close to the limit, that would still
be much better than a direct crash.<br>
<br>
Best<br>
Christopher Schnick<o:p></o:p></p>
<div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 12pt;">On
10/03/2025 18:51, Andy Goryachev
wrote:</span><o:p></o:p></div>
</div>
<blockquote
style="margin-top: 5pt; margin-bottom: 5pt;">
<div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">This
looks to me like it might be
hitting the (native) thread
stack size limit.</span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">c.s.glass.ui.Application::enterNestedEventLoop()
even warns about it:</span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; background: white;"><span
style="font-family: "Iosevka Fixed SS16"; color: rgb(255, 38, 0);">
* An application may enter
several nested loops
recursively. There's no</span><o:p></o:p></div>
<div
style="margin: 0in; background: white;"><span
style="font-family: "Iosevka Fixed SS16"; color: rgb(255, 38, 0);">
* limit of recursion other
than that imposed by the
native stack size.</span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";">-andy</span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
style="margin: 0in; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt; font-family: "Iosevka Fixed SS16";"> </span><o:p></o:p></div>
<div
id="mail-editor-reference-message-container">
<div>
<div>
<div
style="border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) currentcolor currentcolor; border-image: none; padding: 3pt 0in 0in;">
<p class="MsoNormal"
style="margin: 0in 0in 12pt; font-size: 10pt; font-family: Aptos, sans-serif;"><b><span
style="font-size: 12pt;">From:<span class="Apple-converted-space"> </span></span></b><span
style="font-size: 12pt;">openjfx-dev<span class="Apple-converted-space"> </span><a
href="mailto:openjfx-dev-retn@openjdk.org"
style="color: blue; text-decoration: underline;" moz-do-not-send="true"><openjfx-dev-retn@openjdk.org></a><span
class="Apple-converted-space"> </span>on behalf of Martin Fox<span
class="Apple-converted-space"> </span><a
href="mailto:martinfox656@gmail.com"
style="color: blue; text-decoration: underline;" moz-do-not-send="true"><martinfox656@gmail.com></a><br>
<b>Date:<span
class="Apple-converted-space"> </span></b>Monday, March 10, 2025 at
10:10<br>
<b>To:<span
class="Apple-converted-space"> </span></b>Christopher Schnick<span
class="Apple-converted-space"> </span><a
href="mailto:crschnick@xpipe.io"
style="color: blue; text-decoration: underline;" moz-do-not-send="true"><crschnick@xpipe.io></a><br>
<b>Cc:<span
class="Apple-converted-space"> </span></b>OpenJFX<span
class="Apple-converted-space"> </span><a
href="mailto:openjfx-dev@openjdk.org"
style="color: blue; text-decoration: underline;" moz-do-not-send="true"><openjfx-dev@openjdk.org></a><br>
<b>Subject:<span
class="Apple-converted-space"> </span></b>Re: JVM crashes on macOS when
entering too many
nested event loops</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"
style="margin: 0in 0in 12pt; font-size: 10pt; font-family: Aptos, sans-serif;"><span
style="font-size: 11pt;">Hi Christopher,<br>
<br>
I was able to
reproduce this crash.
I wrote a small
routine that
recursively calls
itself in a runLater
block and then enters
a nested event loop.
The program crashes
when creating loop
254. I’m not sure
where that limit comes
from so it’s possible
that consuming some
other system resource
could lower it. I
couldn’t see any good
way to determine how
many loops are active
by looking at the
crash report since it
doesn’t show the
entire call stack.<br>
I did a quick trial on
Linux and was able to
create a lot more
loops (over 600) but
then started seeing
erratic behavior and
errors coming from the
Java VM. The behavior
was variable unlike on
the Mac which always
crashes when creating
loop 254.<br>
<br>
Martin<br>
<br>
> On Mar 7, 2025,
at 6:24</span><span
style="font-size: 11pt; font-family: Arial, sans-serif;"> </span><span
style="font-size: 11pt;">AM, Christopher Schnick<span
class="Apple-converted-space"> </span><a
href="mailto:crschnick@xpipe.io"
style="color: blue; text-decoration: underline;" moz-do-not-send="true"><crschnick@xpipe.io></a><span
class="Apple-converted-space"> </span>wrote:<br>
><span
class="Apple-converted-space"> </span><br>
> Hello,<br>
><span
class="Apple-converted-space"> </span><br>
> I have attached a
JVM fatal error log
that seemingly was
caused by our JavaFX
application entering
too many nested event
loops, which macOS
apparently doesn't
like.<br>
><span
class="Apple-converted-space"> </span><br>
> As far as I know,
there is no upper
limit defined on how
often an event loop
can be nested, so I
think this is a bug
that can occur in rare
situations.<br>
><span
class="Apple-converted-space"> </span><br>
> Best<br>
> Christopher
Schnick<hs_err_pid.txt></span></p>
</div>
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