On Mon, 16 Sep 2024 06:16:56 GMT, Jaikiran Pai <j...@openjdk.org> wrote:
>> src/java.base/share/native/libjli/java.c line 38: >> >>> 36: * One job of the launcher is to remove command line options which the >>> 37: * vm does not understand and will not process. These options include >>> 38: * options which select which style of vm is run (e.g. -client and >> >> Aren't these the only options now? > > Right now, in mainline, the launcher code in `CheckJvmType` function > additionally also checks for the presence of `-XXaltjvm` launcher option. > Just like for `-server`, `-client` options, this `CheckJvmType` function also > strips the `-XXaltjvm` option from the options that are passed along to the > JVM. > > Specifically, in mainline, right now the following appears to be functional: > > > <JDK_24>/bin/java -XXaltjvm=<JDK_22>/lib/server/ -version > > will load and print the Java 22 VM output: > > > openjdk version "22" 2024-03-19 > OpenJDK Runtime Environment (build 22+36-2370) > OpenJDK 64-Bit Server VM (build 22+36-2370, mixed mode, sharing) > > > i.e. the launcher from mainline JDK launches the altjvm from JDK 22. > `CheckJvmType` in the launcher code, is where this parsing and stripping of > `-XXaltjvm` is currently happening. > > (There's also some hotspot VM side code which appears to be parsing a > `-Dsun.java.launcher.is_altjvm=` option to detect this `-XXaltjvm` usage, but > as far as I can see the launcher no where sets this > `-Dsun.java.launcher.is_altjvm=` when `-XXaltjvm` is used. So, I think, this > needs a separate investigation of its own) The property is used by the gtest launcher - see comments in [JDK-8171508](https://bugs.openjdk.org/browse/JDK-8171508) This is all a lot more complicated than I had thought it was. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20997#discussion_r1761027867
