With the current bits in jdk9/hs and graal-core, the following bootstrapping command works in terms of replacing Graal in the JDK:
java -server -XX:+UnlockExperimentalVMOptions --module-path=/Users/dsimon/hs/truffle/mxbuild/modules/com.oracle.truffle.truffle_api.jar --upgrade-module-path=/Users/dsimon/hs/graal-core/mxbuild/modules/jdk.vm.compiler.jar --patch-module=jdk.vm.compiler=.jar -XX:+UseJVMCICompiler -XX:+BootstrapJVMCI -version However, the --patch-module + --upgrade-module-path trick[1] we’re using to replace the version of Graal in the JDK apparently only works due to a bug that will be fixed at some point. From Mandy Chung: "-—patch-module is to patch a module to replace or add content of that module and yes it disables the hash checking on the patched module. However, it’s not intended to allow it to combine with —-upgrade-module-path as you did, to change the module dependences." Given all the continuing flux around jigsaw, we cannot be sure that developing and using GitHub Graal on JDK 9 is stable until jigsaw is stable. -Doug [1] https://bugs.openjdk.java.net/browse/JDK-8171448?focusedCommentId=14046154&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14046154 > On 16 Feb 2017, at 10:17, Andrew Haley <a...@redhat.com> wrote: > > On 15/02/17 21:56, Christian Thalinger wrote: >> >>> On Feb 14, 2017, at 4:38 AM, Andrew Haley <a...@redhat.com> wrote: >>> >>> On 14/02/17 14:37, Alan Bateman wrote: >>>> --patch-module can be used to patch any module in the boot layer. So if >>>> you are looking to override or add classes then --patch-module should work. >>> >>> Aha! Thanks, >> >> Does it? > > Not quite. The problem is that the service loader finds classes in > the Hotspot copy of Graal which don't exist in the external copy, and > chaos ensues. > > I suppose the only way to make it work is to replace the copy of Graal > in HotSpot, but I don't think that's a trivial thing to do. > > Andrew. >