« Return to Thread: [67cat][debugger] Expression evaluation issue?
Re: [67cat][debugger] Expression evaluation issue?
by Martin Entlicher
::
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You can always evaluate "subtract" and nothing will be changed. There's
no need to evaluate "subtract--", am I right?
Mouse over "subtract" in expression "paramsCount - (subtract--)" where
nothing is selected, only "subtract" is evaluate, which does not change
anything.
What would you expect debugger would do if you select "subtract = 10"
end evaluate?
-Martin
Eric M. Smith wrote:
> I'm sorry, but IMO that's about the most useless thing I can think
> of. What you've basically said is that if you're going to debug your
> application, if you want to check on something, you've just changed
> the state of your program. This renders your debugging session
> absolutely useless.
>
> Every debugger I've worked with separates evaluate from assign so a
> person can evaluate the state of the running program at any time, and
> as frequently as needed, but only assign a new value when explicitly
> doing so.
>
> I experienced this bug by mousing over the code and doing an
> evaluation of the value under the mouse pointer. In my case, it threw
> an NPE which trashed my debugging session because it bypassed the code
> I was trying to test.
>
> I can't see how this could possibly be beneficial because if what you
> say holds true, I can't evaluate the parameter values prior to
> stepping into the module.
>
> Eric
>
> Martin Entlicher wrote:
>> Claudiu, the expression that you evaluate have the same effect as if
>> you execute it. This was implemented intentionally, since in the past
>> many users complained that evaluation of "a = 10" does not set the
>> value to "a".
>> You're evaluating "subtract--", which is exactly the same as
>> "subtract = subtract - 1". You're setting a new value to subtract, so
>> no surprise that it change the program.
>>
>> The same effect have method evaluation. If you have a method:
>> doSubtract() {
>> subtract--;
>> }
>> and evaluate "doSubtract()", the value of "subtract" will also change
>> and there's nothing we can do about that.
>>
>> Therefore we've decided that debugger will behave as consistently and
>> transparently as possible and evaluate everything as if it was executed.
>>
>> Does that make sense?
>> Martin
>>
>> Claudiu Bulcu wrote:
>>> Hi,
>>>
>>> Have you seen the following before?
>>>
>>> I have an expression like this:
>>>
>>> paramsCount - (subtract--)
>>>
>>> both being int variables.
>>>
>>> Every time I hover over the selected expression (quick evaluation),
>>> the result is incremented over and over again. Is this by design. I
>>> would expect that expression being evaluated to the same value,
>>> regardless what the subtract value becomes later in my code.
>>>
>>> Try this at home with NB 6.7 RC3.
>>>
>>> Regards,
>>>
>>> --
>>> Claudiu Bulcu
>>> Software Developer
>>>
>>> "A wise person will listen and take in more instruction, and a man
>>> of understanding is the one who acquires skillful direction"
>>>
>>> http://udy.smugmug.com
>>> www.bulcu.ro <http://www.bulcu.ro>
>>
no need to evaluate "subtract--", am I right?
Mouse over "subtract" in expression "paramsCount - (subtract--)" where
nothing is selected, only "subtract" is evaluate, which does not change
anything.
What would you expect debugger would do if you select "subtract = 10"
end evaluate?
-Martin
Eric M. Smith wrote:
> I'm sorry, but IMO that's about the most useless thing I can think
> of. What you've basically said is that if you're going to debug your
> application, if you want to check on something, you've just changed
> the state of your program. This renders your debugging session
> absolutely useless.
>
> Every debugger I've worked with separates evaluate from assign so a
> person can evaluate the state of the running program at any time, and
> as frequently as needed, but only assign a new value when explicitly
> doing so.
>
> I experienced this bug by mousing over the code and doing an
> evaluation of the value under the mouse pointer. In my case, it threw
> an NPE which trashed my debugging session because it bypassed the code
> I was trying to test.
>
> I can't see how this could possibly be beneficial because if what you
> say holds true, I can't evaluate the parameter values prior to
> stepping into the module.
>
> Eric
>
> Martin Entlicher wrote:
>> Claudiu, the expression that you evaluate have the same effect as if
>> you execute it. This was implemented intentionally, since in the past
>> many users complained that evaluation of "a = 10" does not set the
>> value to "a".
>> You're evaluating "subtract--", which is exactly the same as
>> "subtract = subtract - 1". You're setting a new value to subtract, so
>> no surprise that it change the program.
>>
>> The same effect have method evaluation. If you have a method:
>> doSubtract() {
>> subtract--;
>> }
>> and evaluate "doSubtract()", the value of "subtract" will also change
>> and there's nothing we can do about that.
>>
>> Therefore we've decided that debugger will behave as consistently and
>> transparently as possible and evaluate everything as if it was executed.
>>
>> Does that make sense?
>> Martin
>>
>> Claudiu Bulcu wrote:
>>> Hi,
>>>
>>> Have you seen the following before?
>>>
>>> I have an expression like this:
>>>
>>> paramsCount - (subtract--)
>>>
>>> both being int variables.
>>>
>>> Every time I hover over the selected expression (quick evaluation),
>>> the result is incremented over and over again. Is this by design. I
>>> would expect that expression being evaluated to the same value,
>>> regardless what the subtract value becomes later in my code.
>>>
>>> Try this at home with NB 6.7 RC3.
>>>
>>> Regards,
>>>
>>> --
>>> Claudiu Bulcu
>>> Software Developer
>>>
>>> "A wise person will listen and take in more instruction, and a man
>>> of understanding is the one who acquires skillful direction"
>>>
>>> http://udy.smugmug.com
>>> www.bulcu.ro <http://www.bulcu.ro>
>>
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