DO NOT REPLY [Bug 26049] New: - Incorrect verification of class files

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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=26049

Incorrect verification of class files

           Summary: Incorrect verification of class files
           Product: BCEL
           Version: 5.1
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: Normal
          Priority: Other
         Component: Main
        AssignedTo: [email protected]
        ReportedBy: [email protected]


Hi,

JustIce indicates that the storing of a newly created object in a local before
calling it's constructor as an error.  However, this is incorrect as the local
is not accessed along any control flow path before the constructor is called. 
This is also safe in a multithreaded setting. Also, the same class file is well
interpreted by java interpreters from SUN, Blackdown, and IBM.  Moreover, there
is no restriction on handling (not using) of uninitialized objects in the JVM spec.

ASM output of the correponding class file and JustIce' output are inlined.

public static main ([Ljava/lang/String;)V
    NEW excpsync
    ASTORE 1
    ALOAD 1
    INVOKESPECIAL excpsync <init> ()V
    ALOAD 1
    ASTORE 1
    NEW java/lang/Thread
    ASTORE 2
    ALOAD 2
    ALOAD 1
    INVOKESPECIAL java/lang/Thread <init> (Ljava/lang/Runnable;)V
    ALOAD 2
    INVOKEVIRTUAL java/lang/Thread start ()V
    NEW java/lang/Thread
    ASTORE 2
    NEW f
    ASTORE 3
    ALOAD 3
    INVOKESPECIAL f <init> ()V
    ALOAD 2
    ALOAD 3
    INVOKESPECIAL java/lang/Thread <init> (Ljava/lang/Runnable;)V
    ALOAD 2
    INVOKEVIRTUAL java/lang/Thread start ()V
    LDC "Hi"
    ASTORE 2
    ALOAD 1
    ALOAD 2
    PUTFIELD excpsync o Ljava/lang/String;
    ALOAD 2
    PUTSTATIC excpsync t Ljava/lang/String;
    RETURN
    MAXSTACK = 2
    MAXLOCALS = 4

JustIce by Enver Haase, (C) 2001-2002.
<http://bcel.sourceforge.net>
<http://jakarta.apache.org/bcel>

Now verifying: excpsync

Pass 1:
VERIFIED_OK
Passed verification.

Pass 2:
VERIFIED_OK
Passed verification.

Pass 3a, method number 0 ['public void <init>()']:
VERIFIED_OK
Passed verification.

Pass 3b, method number 0 ['public void <init>()']:
VERIFIED_OK
Passed verification.

Pass 3a, method number 1 ['public static void main(String[] arg0)']:
VERIFIED_OK
Passed verification.

Pass 3b, method number 1 ['public static void main(String[] arg0)']:
VERIFIED_REJECTED
Constraint violated in method 'public static void main(String[] arg0)':
Instruction ASTORE constraint violated: Working on an uninitialized object
'<UNINITIALIZED OBJECT OF TYPE 'excpsync'>'.
InstructionHandle:    3: astore_1[76](1)

Execution Frame:
Local Variables:
0: java.lang.String[]
1: <unknown object>
2: <unknown object>
3: <unknown object>
OperandStack:
Slots used: 1 MaxStack: 2.
<UNINITIALIZED OBJECT OF TYPE 'excpsync'> (Size: 1)
Execution flow:
   0: new 12	[InstructionContext]
   3: astore_1	[InstructionContext]

Pass 3a, method number 2 ['public void run()']:
VERIFIED_OK
Passed verification.

Pass 3b, method number 2 ['public void run()']:
VERIFIED_OK
Passed verification.