Sometimes, and it's not immediately clear when, javacserver leaves behind server.log files in the make/ directory.

One fairly reliable reproducer is the cmp-baseline runs where the file appears to be created around the time the build switches from building the baseline to building the second/comparison JDK. In Oracle/jib speak that's:

jib configure -p linux-x64-cmp-baseline
jib make -p linux-x64-cmp-baseline

For that specific case, the contents of the make/server.log file is:

java.lang.NoClassDefFoundError: javacserver/shared/Result
        at javacserver.server.Server.main(Server.java:84)
Caused by: java.lang.ClassNotFoundException: javacserver.shared.Result
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:528)
        ... 1 more

For this specific case it appears to happen ever since JDK-8297444 back in JDK 20.

There are (at least) two different things that could be explored:

1. Why does the exception get thrown to start with
2. Can/should the server.log file be placed somewhere else instead? Perhaps in the build directory?