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[GR-65777] Adopt "JDK-8344706: Implement JEP 512: Compact Source Files and Instance Main Methods" #11430

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Merged
merged 1 commit into from
Jun 18, 2025
Merged

[GR-65777] Adopt "JDK-8344706: Implement JEP 512: Compact Source Files and Instance Main Methods" #11430

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6 changes: 1 addition & 5 deletions substratevm/mx.substratevm/mx_substratevm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -881,33 +881,29 @@ def _cinterfacetutorial(native_image, args=None):
}
''',
'noArgs': '''
// requires JDK 21 and --enable-preview
public class HelloWorld {
static void main() {
System.out.println(System.getenv("%s"));
}
}
''',
'instance': '''
// requires JDK 21 and --enable-preview
class HelloWorld {
void main(String[] args) {
System.out.println(System.getenv("%s"));
}
}
''',
'instanceNoArgs': '''
// requires JDK 21 and --enable-preview
class HelloWorld {
void main() {
System.out.println(System.getenv("%s"));
}
}
''',
'unnamedClass': '''
// requires JDK 21 and javac --enable-preview --source 21 and native-image --enable-preview
void main() {
System.out.println(System.getenv("%s"));
IO.println(System.getenv("%s"));
}
''',
}
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50 changes: 14 additions & 36 deletions substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/JavaMainWrapper.java
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Expand Up @@ -113,30 +113,22 @@ public static class JavaMainSupport implements ApplicationLayerOnlyImageSingleto

@Platforms(Platform.HOSTED_ONLY.class)
public JavaMainSupport(Method javaMainMethod) throws IllegalAccessException {
if (instanceMainMethodSupported()) {
javaMainMethod.setAccessible(true);
int mods = javaMainMethod.getModifiers();
this.mainNonstatic = !Modifier.isStatic(mods);
this.mainWithoutArgs = javaMainMethod.getParameterCount() == 0;
MethodHandle mainHandle = MethodHandles.lookup().unreflect(javaMainMethod);
MethodHandle ctorHandle = null;
if (mainNonstatic) {
// Instance main
try {
Constructor<?> ctor = ReflectionUtil.lookupConstructor(javaMainMethod.getDeclaringClass());
ctorHandle = MethodHandles.lookup().unreflectConstructor(ctor);
} catch (ReflectionUtil.ReflectionUtilError ex) {
throw UserError.abort(ex, "No non-private zero argument constructor found in class %s", ClassUtil.getUnqualifiedName(javaMainMethod.getDeclaringClass()));
}
int mods = javaMainMethod.getModifiers();
this.mainNonstatic = !Modifier.isStatic(mods);
this.mainWithoutArgs = javaMainMethod.getParameterCount() == 0;
MethodHandle mainHandle = MethodHandles.lookup().unreflect(javaMainMethod);
MethodHandle ctorHandle = null;
if (mainNonstatic) {
// Instance main
try {
Constructor<?> ctor = ReflectionUtil.lookupConstructor(javaMainMethod.getDeclaringClass());
ctorHandle = MethodHandles.lookup().unreflectConstructor(ctor);
} catch (ReflectionUtil.ReflectionUtilError ex) {
throw UserError.abort(ex, "No non-private zero argument constructor found in class %s", ClassUtil.getUnqualifiedName(javaMainMethod.getDeclaringClass()));
}
this.javaMainHandle = mainHandle;
this.javaMainClassCtorHandle = ctorHandle;
} else {
this.mainNonstatic = false;
this.mainWithoutArgs = false;
this.javaMainHandle = MethodHandles.lookup().unreflect(javaMainMethod);
this.javaMainClassCtorHandle = null;
}
this.javaMainHandle = mainHandle;
this.javaMainClassCtorHandle = ctorHandle;
this.javaMainClassName = javaMainMethod.getDeclaringClass().getName();
}

Expand Down Expand Up @@ -199,20 +191,6 @@ public static void invokeMain(String[] args) throws Throwable {
}
}

/**
* Determines whether instance main methodes are enabled. See JDK-8306112: Implementation of JEP
* 445: Unnamed Classes and Instance Main Methods (Preview).
*/
@Platforms(Platform.HOSTED_ONLY.class)
public static boolean instanceMainMethodSupported() {
var previewFeature = ReflectionUtil.lookupClass(true, "jdk.internal.misc.PreviewFeatures");
try {
return previewFeature != null && (Boolean) previewFeature.getDeclaredMethod("isEnabled").invoke(null);
} catch (ReflectiveOperationException e) {
throw VMError.shouldNotReachHere(e);
}
}

@Uninterruptible(reason = "The caller initialized the thread state, so the callees do not need to be uninterruptible.", calleeMustBe = false)
private static int runCore() {
return runCore0();
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36 changes: 24 additions & 12 deletions ...atevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageGeneratorRunner.java
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,7 @@
import com.oracle.svm.core.SubstrateOptions;
import com.oracle.svm.core.option.HostedOptionKey;
import com.oracle.svm.core.option.SubstrateOptionsParser;
import com.oracle.svm.core.util.BasedOnJDKFile;
import com.oracle.svm.core.util.ExitStatus;
import com.oracle.svm.core.util.InterruptImageBuilding;
import com.oracle.svm.core.util.UserError;
Expand Down Expand Up @@ -495,19 +496,9 @@ private int buildImage(ImageClassLoader classLoader) {
* If no C-level main method was found, look for a Java-level main method
* and use our wrapper to invoke it.
*/
if ("main".equals(mainEntryPointName) && JavaMainWrapper.instanceMainMethodSupported()) {
// Instance main method only supported for "main" method name
if ("main".equals(mainEntryPointName)) {
try {
/*
* JDK-8306112: Implementation of JEP 445: Unnamed Classes and
* Instance Main Methods (Preview)
*
* MainMethodFinder will perform all the necessary checks
*/
String mainMethodFinderClassName = "jdk.internal.misc.MethodFinder";
Class<?> mainMethodFinder = ReflectionUtil.lookupClass(false, mainMethodFinderClassName);
Method findMainMethod = ReflectionUtil.lookupMethod(mainMethodFinder, "findMainMethod", Class.class);
javaMainMethod = (Method) findMainMethod.invoke(null, mainClass);
javaMainMethod = findDefaultJavaMainMethod(mainClass);
} catch (InvocationTargetException ex) {
assert ex.getTargetException() instanceof NoSuchMethodException;
throw UserError.abort(ex.getCause(),
Expand Down Expand Up @@ -618,6 +609,27 @@ private int buildImage(ImageClassLoader classLoader) {
return ExitStatus.OK.getValue();
}

/*
* Finds the main method using the {@code jdk.internal.misc.MethodFinder}.
*
* The {@code MethodFinder} was introduced by JDK-8344706 (Implement JEP 512: Compact Source
* Files and Instance Main Methods) and will perform all the necessary checks.
*/
@BasedOnJDKFile("https://github.com/openjdk/jdk/blob/jdk-25+24/src/java.base/share/classes/jdk/internal/misc/MethodFinder.java#L45-L106")
private static Method findDefaultJavaMainMethod(Class<?> mainClass) throws IllegalAccessException, InvocationTargetException {
Class<?> mainMethodFinder = ReflectionUtil.lookupClass(false, "jdk.internal.misc.MethodFinder");
Method findMainMethod = ReflectionUtil.lookupMethod(mainMethodFinder, "findMainMethod", Class.class);
/*
* We are using Method.invoke and throwing checked exceptions on purpose instead of
* ReflectionUtil to issue a proper error message.
*/
Method invoke = (Method) findMainMethod.invoke(null, mainClass);
/*
* Use ReflectionUtil get a Method object with the right accessibility.
*/
return ReflectionUtil.lookupMethod(invoke.getDeclaringClass(), invoke.getName(), invoke.getParameterTypes());
}

private static void reportConflictingOptions(HostedOptionKey<Boolean> o1, HostedOptionKey<?> o2) {
throw UserError.abort("Cannot pass both options: %s and %s", SubstrateOptionsParser.commandArgument(o1, "+"), SubstrateOptionsParser.commandArgument(o2, "+"));
}
Expand Down