Creating JVM
David Holmes
david.holmes at oracle.com
Sun Mar 3 07:26:30 UTC 2019
Try turning on all logging:
-Xlog:all=trace
and see what it shows.
David
-----
On 3/03/2019 11:24 am, Sparse Way wrote:
> Hello,
>
> How does the JVM locate and load java base classes during its creation process?
>
> Since JVM exits at call_initPhase2(TRAPS) in Threads::create_vm without a stack trace or an exception.
>
> hotspot/src/share/vm/runtime/thread.cpp:
>
> ...
> // Phase 2. Module system initialization
> // This will initialize the module system. Only java.base classes
> // can be loaded until phase 2 completes.
> //
> // Call System.initPhase2 after the compiler initialization and jsr292
> // classes get initialized because module initialization runs a lot of java
> // code, that for performance reasons, should be compiled. Also, this will
> // enable the startup code to use lambda and other language features in this
> // phase and onward.
> //
> // After phase 2, The VM will begin search classes from -Xbootclasspath/a.
> static void call_initPhase2(TRAPS) {
> TraceTime timer("Phase2 initialization", TRACETIME_LOG(Info, module, startuptime));
>
> Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
> instanceKlassHandle klass (THREAD, k);
>
> JavaValue result(T_INT);
> JavaCallArguments args;
> args.push_int(DisplayVMOutputToStderr);
> args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
> JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
> vmSymbols::boolean_boolean_int_signature(), &args, CHECK);
> if (result.get_jint() != JNI_OK) {
> vm_exit_during_initialization(); // no message or exception
> }
>
> universe_post_module_init();
> }
> ...
>
> Specifically when calling java.lang.System.initPhase2(boolean printToStderr, boolean printStackTrace) statically.
> JVM options: "-Djava.home=" + jre,
> "--patch-module=" + ext + "java.base=src"
> Replacing --patch-module with -Xbootclasspath/a will not help.
>
> I am not sure if base classes are loaded in the first place.
>
> Best regards
>
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