[External] : Re: Wrong error reported

[Øystein Myhre Andersen]

Thank you.

P.S. I have worked with code generators since the 1960s and experienced
several times staring at the code without seeing the error. It was the
method type descriptor that was wrong.

- Øystein


On Mon, Jun 17, 2024 at 3:01 PM Adam Sotona <adam.sotona at oracle.com> wrote:

> 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>
> wrote:
>
> 15: INVOKESPECIAL consumes 3 objects from stack
>
>
>
>
>
> *From: *classfile-api-dev <classfile-api-dev-retn at openjdk.org> on behalf
> of Øystein Myhre Andersen <o.myhre at gmail.com>
> *Date: *Monday, 10 June 2024 at 10:07
> *To: *classfile-api-dev <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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