3. The fact that Fiji hangs at startup on some systems with the new launcher, but not with the old launcher, is a critical new bug, which we still don't understand. @haesleinhuepf On your affected system, please rename ImageJ-win64.exe to debug.exe and run it, to see what's happening in more detail. If there's nothing helpful there, you can then generate a thread dump (ctrl+pause) to see if things are deadlocked on the Java side. Please paste any interesting findings here on this issue.

I'm seeing the above mentioned quick crash issue after updating just now (Windows 10 64bit Insider build 20185). Following is the console output after renaming to debug.exe:

Detected Fiji
Using JRE from ImageJ.cfg: D:\bin\tools\fiji/jre
Found Java options in ImageJ.cfg: '-Xmx7560m -cp ij.jar'
JRE not found in 'D:\bin\tools\fiji/jre'
JAVA_HOME contains a JRE: 'D:\bin\tools\fiji/java/win64/jdk1.8.0_172//jre'
java -Xmx7560m -Dpython.cachedir.skip=true -Dplugins.dir=D:\\bin\\tools\\fiji -Xincgc -XX:PermSize=128m -Dsun.java.command=ImageJ -Djava.class.path=D:\\bin\\tools\\fiji/jars/imagej-launcher-5.0.3.jar -Dimagej.dir=D:\\bin\\tools\\fiji -Dij.dir=D:\\bin\\tools\\fiji -Dfiji.dir=D:\\bin\\tools\\fiji -Dfiji.defaultLibPath=bin/server/jvm.dll -Dfiji.executable=D:\\bin\\tools\\fiji\\debug.exe -Dij.executable=D:\\bin\\tools\\fiji\\debug.exe -Djava.library.path=D:\\bin\\tools\\fiji/lib/win64;D:\\bin\\tools\\fiji/mm/win64 -Dsun.java2d.noddraw=true -Dij.debug=true -Dscijava.log.level=debug net.imagej.launcher.ClassLauncher -classpath D:\\bin\\tools\\fiji/jars/ij-1.53c.jar fiji.Main -port7
Using JAVA_HOME D:\bin\tools\fiji/java/win64/jdk1.8.0_172//jre
Opening Java library D:\bin\tools\fiji/java/win64/jdk1.8.0_172//jre/bin/server/jvm.dll
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option PermSize=128m; support was removed in 8.0
Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release
Adding option: -Djava.home=D:\bin\tools\fiji/java/win64/jdk1.8.0_172/
Launching main class fiji.Main with parameters [-port7]
Class loader = sun.misc.Launcher$AppClassLoader@c387f44
java.lang.ClassNotFoundException: fiji.Main
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        at net.imagej.launcher.ClassLauncher.launch(ClassLauncher.java:264)
        at net.imagej.launcher.ClassLauncher.run(ClassLauncher.java:198)
        at net.imagej.launcher.ClassLauncher.main(ClassLauncher.java:89)
java.lang.NullPointerException
        at net.imagej.launcher.ClassLauncher.launch(ClassLauncher.java:281)
        at net.imagej.launcher.ClassLauncher.run(ClassLauncher.java:198)
        at net.imagej.launcher.ClassLauncher.main(ClassLauncher.java:89)

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Fixes https://github.com/mochajs/mocha/issues/4390