On Thu, 8 May 2025 11:22:30 GMT, Alan Bateman <[email protected]> wrote:
> Implementation changes for [JEP 500: Prepare to Make Final Mean > Final](https://openjdk.org/jeps/500). > > Field.set (and Lookup.unreflectSetter) are changed to allow/warn/debug/deny > when mutating a final instance field. JFR event recorded if final field > mutated. Spec updates to Field.set, Field.setAccessible and Module.addOpens > to align with the proposal in the JEP. > > HotSpot is updated to add support for the new command line options. To aid > diagnosability, -Xcheck:jni reports a fatal error when a mutating a final > field with JNI, and -Xlog:jni=debug can help identity when JNI code mutates > finals. For now, JNI code is allowed to set the "write-protected" fields > System.in/out/err, we can re-visit once we change the > System.setIn/setOut/setErr methods to not use JNI (I prefer to keep this > separate to this PR because there is a small startup regression to address > when changing System.setXXX). > > There are many new tests. A small number of existing tests are changed to run > /othervm as reflectively opening a package isn't sufficient. Changing the > tests to /othervm means that jtreg will launch the agent with the command > line options to open the package. > > Testing: tier1-6 Duplicate Code in Field.java In the java.lang.reflect.Field class, the set* methods (such as set, setBoolean, setByte, etc.) contain a lot of duplicate code for handling access control of final fields. Recommendation: Consider creating a generic helper method to handle the access control check for final fields, thus reducing code duplication. @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization public void set(Object obj, Object value) throws IllegalArgumentException, IllegalAccessException { handleFinalFieldModification( Reflection.getCallerClass(), obj, () -> getOverrideFieldAccessor() .set(obj, value)); } @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization public void setBoolean(Object obj, boolean z) throws IllegalArgumentException, IllegalAccessException { handleFinalFieldModification( Reflection.getCallerClass(), obj, () -> getOverrideFieldAccessor() .setBoolean(obj, z)); } @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization public void setByte(Object obj, byte b) throws IllegalArgumentException, IllegalAccessException { handleFinalFieldModification( Reflection.getCallerClass(), obj, () -> getOverrideFieldAccessor() .setByte(obj, b)); } @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization public void setChar(Object obj, char c) throws IllegalArgumentException, IllegalAccessException { handleFinalFieldModification( Reflection.getCallerClass(), obj, () -> getOverrideFieldAccessor() .setChar(obj, c)); } @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization public void setShort(Object obj, short s) throws IllegalArgumentException, IllegalAccessException { handleFinalFieldModification( Reflection.getCallerClass(), obj, () -> getOverrideFieldAccessor() .setShort(obj, s)); } @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization public void setInt(Object obj, int i) throws IllegalArgumentException, IllegalAccessException { handleFinalFieldModification( Reflection.getCallerClass(), obj, () -> getOverrideFieldAccessor() .setInt(obj, i)); } @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization public void setLong(Object obj, long l) throws IllegalArgumentException, IllegalAccessException { handleFinalFieldModification( Reflection.getCallerClass(), obj, () -> getOverrideFieldAccessor() .setLong(obj, l)); } @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization public void setFloat(Object obj, float f) throws IllegalArgumentException, IllegalAccessException { handleFinalFieldModification( Reflection.getCallerClass(), obj, () -> getOverrideFieldAccessor() .setFloat(obj, f)); } @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization public void setDouble(Object obj, double d) throws IllegalArgumentException, IllegalAccessException { handleFinalFieldModification( Reflection.getCallerClass(), obj, () -> getOverrideFieldAccessor() .setDouble(obj, d)); } private interface Setter { void run() throws IllegalAccessException; } @ForceInline private void handleFinalFieldModification(Class<?> callerClass, Object obj, Setter setter) throws IllegalAccessException { if (!override) { checkAccess(callerClass, obj); setter.run(); return; } if (!isFinalInstanceInNormalClass()) { setter.run(); return; } // final field in normal class handling preSetFinal(callerClass, obj); setter.run(); postSetFinal(callerClass); } ------------- PR Comment: https://git.openjdk.org/jdk/pull/25115#issuecomment-3322635579
