[External] : Re: Wrong error reported

[Adam Sotona]

objectref and two arguments are three object to consume.

From: Øystein Myhre Andersen <o.myhre at gmail.com>
Date: Monday, 17 June 2024 at 14:58
To: Adam Sotona <adam.sotona at oracle.com>
Cc: classfile-api-dev <classfile-api-dev at openjdk.org>
Subject: [External] : Re: Wrong error reported

You say “15: INVOKESPECIAL" consumes 3 objects from stack ”.

I don't see how that could be the case. The jvm spec says:

               ..., objectref, [arg1, [arg2 ...]] →



In my case I have one argument and INVOKESPECIAL should consume TWO objects.



In detail

Just before the INVOKESPECIAL the operand stack looks like this:



                      this.SL, P_TXT2, P_TXT2, this.P_T



where

    - this.SL is a pointer to the argument to the constructor.

    - P_TXT2 is the implicit object reference to the class being constructed.

   - After that, the rest of the operand stack which should not be touched



The INVOKESPECIAL should in this case consume TWO objects from the operand stack.

See the method type: (Lsimula/runtime/RTS_RTObject;Lsimula/runtime/RTS_TXT;)V}

As I mentioned earlier, the javac compiler produces the same code.



- Øystein Myhre Andersen

On Mon, Jun 17, 2024 at 1:09 PM Adam Sotona <adam.sotona at oracle.com<mailto:adam.sotona at oracle.com>> wrote:
15: INVOKESPECIAL consumes 3 objects from stack


From: classfile-api-dev <classfile-api-dev-retn at openjdk.org<mailto:classfile-api-dev-retn at openjdk.org>> on behalf of Øystein Myhre Andersen <o.myhre at gmail.com<mailto:o.myhre at gmail.com>>
Date: Monday, 10 June 2024 at 10:07
To: classfile-api-dev <classfile-api-dev at openjdk.org<mailto:classfile-api-dev at openjdk.org>>
Subject: Wrong error reported
I got:


Exception in thread "main" java.lang.IllegalArgumentException: Operand stack underflow at bytecode offset 26 of method _STM()

- max stack: 65535

max locals: 65535

attributes: []

//stack map frame @0: {locals: [simulaTestPrograms/adHoc01_P_TXT2], stack: []}

0: {opcode: ALOAD_0, slot: 0}

1: {opcode: GETFIELD, owner: simulaTestPrograms/adHoc01_P_TXT2, field name: P_T, field type: Lsimula/runtime/RTS_TXT;}

4: {opcode: NEW, type: simulaTestPrograms/adHoc01_P_TXT2}

7: {opcode: DUP}

8: {opcode: ALOAD_0, slot: 0}

9: {opcode: GETFIELD, owner: simula/runtime/RTS_RTObject, field name: _SL, field type: Lsimula/runtime/RTS_RTObject;}

12: {opcode: CHECKCAST, type: simulaTestPrograms/adHoc01}

15: {opcode: INVOKESPECIAL, owner: simulaTestPrograms/adHoc01_P_TXT2, method name: <init>, method type: (Lsimula/runtime/RTS_RTObject;Lsimula/runtime/RTS_TXT;)V}

18: {opcode: GETFIELD, owner: simulaTestPrograms/adHoc01_P_TXT2, field name: _RESULT, field type: Lsimula/runtime/RTS_TXT;}

21: {opcode: LDC, constant value: Abra}

23: {opcode: INVOKESTATIC, owner: simulaTestPrograms/adHoc01_P_TXT2, method name: _ASGSTR, method type: (Lsimula/runtime/RTS_TXT;Ljava/lang/String;)Lsimula/runtime/RTS_TXT;}

26: {opcode: INVOKESTATIC, owner: simulaTestPrograms/adHoc01_P_TXT2, method name: _ASGTXT, method type: (Lsimula/runtime/RTS_TXT;Lsimula/runtime/RTS_TXT;)Lsimula/runtime/RTS_TXT;}

29: {opcode: POP}

30: {opcode: ALOAD_0, slot: 0}

31: {opcode: INVOKEVIRTUAL, owner: simulaTestPrograms/adHoc01_P_TXT2, method name: EBLK, method type: ()V}

34: {opcode: ALOAD_0, slot: 0}

35: {opcode: ARETURN}

Then I monitor the operand stack as follows:

    0: {opcode: ALOAD_0, slot: 0}
    1: {opcode: GETFIELD, owner: simulaTestPrograms/adHoc01_P_TXT2, field name: P_T, field type: Lsimula/runtime/RTS_TXT;}
==> STACK: this.P_T

    4: {opcode: NEW, type: simulaTestPrograms/adHoc01_P_TXT2}
==> STACK: P_TXT2, this.P_T

    7: {opcode: DUP}
==> STACK: P_TXT2, P_TXT2, this.P_T

    8: {opcode: ALOAD_0, slot: 0}
    9: {opcode: GETFIELD, owner: simula/runtime/RTS_RTObject, field name: _SL, field type: Lsimula/runtime/RTS_RTObject;}
    12: {opcode: CHECKCAST, type: simulaTestPrograms/adHoc01}
==> STACK: this.SL, P_TXT2, P_TXT2, this.P_T

    15: {opcode: INVOKESPECIAL, owner: simulaTestPrograms/adHoc01_P_TXT2, method name: <init>, method type: (Lsimula/runtime/RTS_RTObject;Lsimula/runtime/RTS_TXT;)V}
==> STACK: P_TXT2, this.P_T

    18: {opcode: GETFIELD, owner: simulaTestPrograms/adHoc01_P_TXT2, field name: _RESULT, field type: Lsimula/runtime/RTS_TXT;}
==> STACK: P_TXT2.RESULT, this.P_T

    21: {opcode: LDC, constant value: Abra}
==> STACK: "Abra", P_TXT2.RESULT, this.P_T

    23: {opcode: INVOKESTATIC, owner: simulaTestPrograms/adHoc01_P_TXT2, method name: _ASGSTR, method type: (Lsimula/runtime/RTS_TXT;Ljava/lang/String;)Lsimula/runtime/RTS_TXT;}
==> STACK: Return-value-1, this.P_T

    26: {opcode: INVOKESTATIC, owner: simulaTestPrograms/adHoc01_P_TXT2, method name: _ASGTXT, method type: (Lsimula/runtime/RTS_TXT;Lsimula/runtime/RTS_TXT;)Lsimula/runtime/RTS_TXT;}
==> STACK: Return-value-2

    29: {opcode: POP}
==> STACK:

    30: {opcode: ALOAD_0, slot: 0}
    31: {opcode: INVOKEVIRTUAL, owner: simulaTestPrograms/adHoc01_P_TXT2, method name: EBLK, method type: ()V}
    34: {opcode: ALOAD_0, slot: 0}
    35: {opcode: ARETURN}

This shows that the error 'Operand stack underflow at bytecode offset 26 of method _STM()' is wrong.

I have also compiled it fram java source:

public adHoc01_P_TXT2 _STM() {

// JavaLine 45 <== SourceLine 6

_ASGTXT(P_T, _ASGSTR(new adHoc01_P_TXT2((_CUR._SL))._RESULT, "Abra") );

EBLK();

return (this);

} // End of Procedure BODY

Which compiles to the same byte-code. AND it executes correctly.
Is there something I'm not  seeing here ?

- Regards, Øystein Myhre Andersen



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