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  1. JDK
  2. JDK-8168655

Interface has an abstract synchronized method - no errors are thrown at runtime

    Details

    • Subcomponent:
    • CPU:
      generic
    • OS:
      generic

      Description

      FULL PRODUCT VERSION :
      Java(TM) SE Runtime Environment (build 1.8.0_102-b14)
      Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)
      Java(TM) SE Runtime Environment (build 1.8.0_65-b17)
      Java HotSpot(TM) Server VM (

      FULL OS VERSION :
      Darwin mac-esxi-38 12.5.0 Darwin Kernel Version 12.5.0: Sun Sep 29 13:33:47 PDT 2013; root:xnu-2050.48.12~1/RELEASE_X86_64 x86_64
      Linux intellij-linux-app39-70 3.19.0-69-generic #77~14.04.1-Ubuntu SMP

      A DESCRIPTION OF THE PROBLEM :
      According the JVM specification (4.6): "If a method of a class or interface has its ACC_ABSTRACT flag set, it must not have any of its ACC_PRIVATE, ACC_STATIC, ACC_FINAL, ACC_SYNCHRONIZED, ACC_NATIVE, or ACC_STRICT flags set."
      However, JVM loads interfaces declaring abstract+synchronized method (and classes implementing these interfaces) without any errors.

      It can be observed on the example below.
      This example provides the interface testMethodsIntfFlags_4I.j with abstract+synchronized method, the class testMethodsIntfFlags_4C.j implementing this interface and the class Test.java which tries to instantiate testMethodsIntfFlags_4C. The interface and the class were written in Jasmin (see http://jasmin.sourceforge.net)



      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      1) compile testMethodsIntfFlags_4I.j and testMethodsIntfFlags_4C.j using jasmin
      2) compile and run Test.java

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      Expected: testMethodsIntfFlags_4C won't be instantiated and ClassFormatError (or VerifyError) will be thrown

      Actual: testMethodsIntfFlags_4C is loaded without any errors
      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      testMethodsIntfFlags_4I.j

        .interface testMethodsIntfFlags_4I
        .super java/lang/Object
        .method public abstract synchronized test(I)I
        .end method
      --------------------8<--------------------

      testMethodsIntfFlags_4C.j

      .class public testMethodsIntfFlags_4C
      .super java/lang/Object
      .implements testMethodsIntfFlags_4I
      ;
      ; standard initializer
      .method public <init>()V
         aload_0
         invokenonvirtual java/lang/Object/<init>()V
         return
      .end method
       
      ; test
      .method public test(I)I
         .limit stack 2
         .limit locals 2
         iload_1
         ireturn
      .end method
      --------------------8<--------------------

      Test.java

      public class Test {

          public static void main(String[] args) {

              System.out.println("Verify: public abstract synchronized interface method");
              try {
                  Class cl = Class.forName("testMethodsIntfFlags_4C");
                  cl.newInstance();
                  return failed("class loaded and instantiated");
              } catch (ClassFormatError e) {
                  System.out.println("caught ClassFormatError (expected)");
              } catch (Throwable e) {
                  System.out.println("caught " + e);
              }
          }
      }

      ---------- END SOURCE ----------

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            • Assignee:
              Unassigned
              Reporter:
              webbuggrp Webbug Group
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              • Created:
                Updated:
                Resolved: