ContextPart>>printOn: prints incorrect line

> I have observe strange behavior of MethodContext>>printOn: and
> ContextPart>>currentLineInFile
>
> Eval [
> thisContext print.
> 1.
> ]
>
> This code outputs: UndefinedObject>>executeStatements (test.st:3),
> line is incorrect, I think it should be 2.
>
> Eval [
> thisContext currentLineInFile printNl.
> 1.
> ]
>
> This code outputs: 2, as expected. I look at the
> MethodContext>>printOn: method and there is
> ContextPart>>currentLineInFile called, so why it outputs different
> line number?

> On 07/14/2011 08:25 PM, Ladislav Marek wrote:
>> I have observe strange behavior of MethodContext>>printOn: and
>> ContextPart>>currentLineInFile
>>
>> Eval [
>>       thisContext print.
>>       1.
>> ]
>>
>> This code outputs: UndefinedObject>>executeStatements (test.st:3),
>> line is incorrect, I think it should be 2.
>>
>> Eval [
>>       thisContext currentLineInFile printNl.
>>       1.
>> ]
>>
>> This code outputs: 2, as expected. I look at the
>> MethodContext>>printOn: method and there is
>> ContextPart>>currentLineInFile called, so why it outputs different
>> line number?
>
> It's an off-by-one error.  This is the compiled bytecode for your first
> example:
>
>    0:  source line 2
>        push Global Variable[0] = ContextPart
>    2:  send special message #thisContext
>    4:  send selector 1, 0 args = #printNl
>    6:  source line 2
>        pop stack top
>    8:  push 1
>        return stack top
>
> The instruction pointer when sending #printNl is already 6.  The call to
> #currentLineInFile prints erroneously takes the "source line" bytecode at
> address 6 into account, and prints 2+2-1 = 3.
>
> This patch fixes it:
>
> diff --git a/kernel/ContextPart.st b/kernel/ContextPart.st
> index bfcf8d5..dc11dd3 100644
> --- a/kernel/ContextPart.st
> +++ b/kernel/ContextPart.st
> @@ -125,7 +125,7 @@ methods that can be used in inspection or debugging.'>
>         thus making the implementation faster."
>
>        <category: 'debugging'>
> -       ^self method sourceCodeMap at: self ip + 1 ifAbsent: [1]
> +       ^self method sourceCodeMap at: self ip - 1 ifAbsent: [1]
>     ]
>
>     debugger [
>
> Thanks for reporting it!
>
> Paolo
>

> Thanks. Nice explanation.
>
> On Fri, Jul 15, 2011 at 09:52, Paolo Bonzini <[hidden email]> wrote:
>> On 07/14/2011 08:25 PM, Ladislav Marek wrote:
>>> I have observe strange behavior of MethodContext>>printOn: and
>>> ContextPart>>currentLineInFile
>>>
>>> Eval [
>>>       thisContext print.
>>>       1.
>>> ]
>>>
>>> This code outputs: UndefinedObject>>executeStatements (test.st:3),
>>> line is incorrect, I think it should be 2.
>>>
>>> Eval [
>>>       thisContext currentLineInFile printNl.
>>>       1.
>>> ]
>>>
>>> This code outputs: 2, as expected. I look at the
>>> MethodContext>>printOn: method and there is
>>> ContextPart>>currentLineInFile called, so why it outputs different
>>> line number?
>>
>> It's an off-by-one error.  This is the compiled bytecode for your first
>> example:
>>
>>    0:  source line 2
>>        push Global Variable[0] = ContextPart
>>    2:  send special message #thisContext
>>    4:  send selector 1, 0 args = #printNl
>>    6:  source line 2
>>        pop stack top
>>    8:  push 1
>>        return stack top
>>
>> The instruction pointer when sending #printNl is already 6.  The call to
>> #currentLineInFile prints erroneously takes the "source line" bytecode at
>> address 6 into account, and prints 2+2-1 = 3.
>>
>> This patch fixes it:
>>
>> diff --git a/kernel/ContextPart.st b/kernel/ContextPart.st
>> index bfcf8d5..dc11dd3 100644
>> --- a/kernel/ContextPart.st
>> +++ b/kernel/ContextPart.st
>> @@ -125,7 +125,7 @@ methods that can be used in inspection or debugging.'>
>>         thus making the implementation faster."
>>
>>        <category: 'debugging'>
>> -       ^self method sourceCodeMap at: self ip + 1 ifAbsent: [1]
>> +       ^self method sourceCodeMap at: self ip - 1 ifAbsent: [1]
>>     ]
>>
>>     debugger [
>>
>> Thanks for reporting it!
>>
>> Paolo
>>
>

> Patch should be applied in DebugTools package too (just saying to be sure).
>
> diff --git a/packages/debug/DebugTools.st b/packages/debug/DebugTools.st
> index cb41c3b..f7f8695 100644
> --- a/packages/debug/DebugTools.st
> +++ b/packages/debug/DebugTools.st
> @@ -48,7 +48,7 @@ pointer bytecodes to line numbers.'>
>              ifTrue: [MethodLineMapCache := WeakKeyIdentityDictionary new].
>          lineMap := MethodLineMapCache at: method
>                      ifAbsentPut: [method sourceCodeMap].
> -       ^lineMap at: aContext ip + 1 ifAbsent: [1]
> +       ^lineMap at: aContext ip - 1 ifAbsent: [1]
>       ]
>
>       Debugger class>>  on: aProcess [
>

> On 07/15/2011 06:03 PM, Ladislav Marek wrote:
>> Patch should be applied in DebugTools package too (just saying to be
>> sure).
>>
>> diff --git a/packages/debug/DebugTools.st b/packages/debug/DebugTools.st
>> index cb41c3b..f7f8695 100644
>> --- a/packages/debug/DebugTools.st
>> +++ b/packages/debug/DebugTools.st
>> @@ -48,7 +48,7 @@ pointer bytecodes to line numbers.'>
>> ifTrue: [MethodLineMapCache := WeakKeyIdentityDictionary new].
>> lineMap := MethodLineMapCache at: method
>> ifAbsentPut: [method sourceCodeMap].
>> - ^lineMap at: aContext ip + 1 ifAbsent: [1]
>> + ^lineMap at: aContext ip - 1 ifAbsent: [1]
>> ]
>>
>> Debugger class>> on: aProcess [
>>
>
> Right, thanks!