"native" CompileTheWorld became not very useful in JDK 9+, as it supports only classes in "BCP", and can't compile user provided .jar files. there is Java test library in test/hotspot/jtreg/testlibrary/ctw/ which provides the functionality as CTW used to provide. this library is used in our regular testing and can be also bundled into .jar file by its Makefiles and be used as a stand-alone library.