src/share/classes/jdk/internal/org/objectweb/asm/ClassWriter.java

*** 783,798 ****
      public final void visitInnerClass(final String name,
              final String outerName, final String innerName, final int access) {
          if (innerClasses == null) {
              innerClasses = new ByteVector();
          }
          ++innerClassesCount;
!         innerClasses.putShort(name == null ? 0 : newClass(name));
          innerClasses.putShort(outerName == null ? 0 : newClass(outerName));
          innerClasses.putShort(innerName == null ? 0 : newUTF8(innerName));
          innerClasses.putShort(access);
      }
  
      @Override
      public final FieldVisitor visitField(final int access, final String name,
              final String desc, final String signature, final Object value) {
          return new FieldWriter(this, access, name, desc, signature, value);
--- 783,816 ----
      public final void visitInnerClass(final String name,
              final String outerName, final String innerName, final int access) {
          if (innerClasses == null) {
              innerClasses = new ByteVector();
          }
+         // Sec. 4.7.6 of the JVMS states "Every CONSTANT_Class_info entry in the
+         // constant_pool table which represents a class or interface C that is
+         // not a package member must have exactly one corresponding entry in the
+         // classes array". To avoid duplicates we keep track in the intVal field
+         // of the Item of each CONSTANT_Class_info entry C whether an inner
+         // class entry has already been added for C (this field is unused for
+         // class entries, and changing its value does not change the hashcode
+         // and equality tests). If so we store the index of this inner class
+         // entry (plus one) in intVal. This hack allows duplicate detection in
+         // O(1) time.
+         Item nameItem = newClassItem(name);
+         if (nameItem.intVal == 0) {
              ++innerClassesCount;
!             innerClasses.putShort(nameItem.index);
              innerClasses.putShort(outerName == null ? 0 : newClass(outerName));
              innerClasses.putShort(innerName == null ? 0 : newUTF8(innerName));
              innerClasses.putShort(access);
+             nameItem.intVal = innerClassesCount;
+         } else {
+             // Compare the inner classes entry nameItem.intVal - 1 with the
+             // arguments of this method and throw an exception if there is a
+             // difference?
          }
+     }
  
      @Override
      public final FieldVisitor visitField(final int access, final String name,
              final String desc, final String signature, final Object value) {
          return new FieldWriter(this, access, name, desc, signature, value);