Fwd: Two verification missings

[Yuting Chen]

Can anyone help me check whether some errors should be reported by
Hotspots?  The two classes are also attached.

I generated some Java classes from SOOT's Jimple's code. When I re-checked
the code, I noticed that two classes are absolutely not correct. I'd expect
that some errors (e.g., VerifyError) could be thrown during the operations
of the JVMs, but they are not. Can anyone tell me the reasons?

Case 1: A VerifyError is caught by GCJ-Java, but missed by Hotspot.
However, the type-casting between java.lang.String and java.util.Map may be
unsafe. Verification results: (a) Hotspot 7/8/9: OK; (b) GCJ-Java JVM
(1.5.0): Exception in ... Caused by: java.lang.VerifyError: verification
failed at PC 1 in M1433982529S:internalTransform((Ljava.lang.String;)V):
incompatible type on stack ...

The Jimple's code.
public class M1433982529S extends java.lang.Object
{
    protected void internalTransform(java.lang.String)
    {
        java.util.Map r0;

        r0 := @parameter0: java.util.Map;
        staticinvoke <java.lang.Object: boolean
getBoolean(java.util.Map)>(r0);

        return;
    }
}

Decompile the class: javap -verbose M1433982529S
public class M1433982529S
  minor version: 0
  major version: 46
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Utf8               java/lang/Object
   #2 = Utf8               SourceFile
   #3 = Utf8               main
   #4 = Methodref          #15.#13        //
java/lang/Object.getBoolean:(Ljava/util/Map;)Z
   #5 = Utf8               Code
   #6 = Class              #12            // M1433982529S
   #7 = Utf8               getBoolean
   #8 = Utf8               ([Ljava/lang/String;)V
   #9 = Utf8               Jasmin
  #10 = Utf8               internalTransform
  #11 = Utf8               (Ljava/util/Map;)Z
  #12 = Utf8               M1433982529S
  #13 = NameAndType        #7:#11         // getBoolean:(Ljava/util/Map;)Z
  #14 = Utf8               (Ljava/lang/String;)V
  #15 = Class              #1             // java/lang/Object
{
  ...
  protected void internalTransform(java.lang.String);
    descriptor: (Ljava/lang/String;)V
    flags: ACC_PROTECTED
    Code:
      stack=1, locals=2, args_size=2
         0: aload_1
         1: invokestatic  #4                  // Method
java/lang/Object.getBoolean:(Ljava/util/Map;)Z
         4: pop
         5: return
}

Case 2: Hotspot may miss some checking for classes with low version
numbers. I generated two classes for the next Jimple's code: one is with
version 46, and another with version 51 (they are different only in their
version numbers). I ran the two classes on Hotspot9, and one (46) was
accepted and another (51) was rejected (with verifyError). In addition,
when I ran the two classes on GCJ-Java JVMs, both are rejected with
VerifyErrors (...verification failed at PC 6 in
M1433584778S:encodeObject(()V): merging initialized and uninitialized
types...).

public class M1433584778S extends java.lang.Object
{
    private void <init>()
    {
        M1433584778S r0;

        r0 := @this: M1433584778S;
        specialinvoke r0.<java.lang.Object: void <init>()>();
        return;
    }

    public static void encodeObject()
    {
        java.lang.String r1, r2;
        java.lang.Throwable r3;

     label0:
        r1 = new java.lang.String;

     label1:
        return;

     label2:
        r3 := @caughtexception;
        goto label1;

        catch java.lang.RuntimeException from label0 to label1 with label2;

    }
}

Decompile the classes and found that:
public class M1433584778S
  minor version: 0
  major version: 46
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Utf8               ([Ljava/lang/String;)V
   #2 = Utf8               java/lang/Object
   #3 = Utf8               <init>
   #4 = Class              #2             // java/lang/Object
   #5 = NameAndType        #3:#7          // "<init>":()V
   #6 = Class              #14            // java/lang/String
   #7 = Utf8               ()V
   #8 = Utf8               M1433584778S
   #9 = Utf8               Code
  #10 = Utf8               main
  #11 = Utf8               SourceFile
  #12 = Class              #8             // M1433584778S
  #13 = Class              #15            // java/lang/RuntimeException
  #14 = Utf8               java/lang/String
  #15 = Utf8               java/lang/RuntimeException
  #16 = Utf8               Jasmin
  #17 = Methodref          #4.#5          // java/lang/Object."<init>":()V
  #18 = Utf8               encodeObject
{
  ...
  public static void encodeObject();
    descriptor: ()V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=1, locals=1, args_size=0
         0: new           #6                  // class java/lang/String
         3: astore_0
         4: return
         5: astore_0
         6: goto          4
      Exception table:
         from    to  target type
             0     4     5   Class java/lang/RuntimeException
}