Re: dealloc

[Barbara Morris <bmorris@xxxxxxxxxx>]

Lim Hock-Chai wrote:
> Does anybody know what will happen to the memory of myField1 after the
> dealloc myField1_p statement?  Does it become available for used?

The memory is still there, but it is illegal to use it.  But there is no
exception given for illegal use.
      
>  dealloc myField1_p;                                  
>                                   
>  // I'm still able to use it.  
>  // Will the memory get use by other alloc operation because of above
>  // dealloc? 
>  myField2 = %trim(myField2) + 'BBB';                  

The memory could be allocated for some other use at any time.  From
looking at your code, it seems impossible that it could be allocated
again after your dealloc, but the storage might be reallocated for some
other use in the middle of your %trim or concatenation.

Don't play around with deallocated storage.  It's impossible to predict
what bizarre or bad things might happen if you use storage that is not
allocated to you.

Scott's parking lot analogy is a good one.  Imagine leaving your parking
space, driving around the block, and driving back into the parking space
blindfold.  Now imagine what might be happening to the parking space at
the moment you decide to reuse it illegally:
  - it might never have been used again, and you could drive right in
  - it might have been used by someone else, who has already left, and
you could drive right in
  - it might be occupied by another car, and you would dent both your
car and theirs 
  - someone might have dug a deep hole in it, and your car would fall
into the hole
  - someone might be crossing the parking space on foot, and you would
crush them with your car

Just as you wouldn't try this "reuse the parking space" exercise even
for fun, you shouldn't try the "reuse the deallocated pointer" exercise
for fun either.