[Insight-developers] Okay to remove protected helper function, ExceptionObject::UpdateWhat()?

[Niels Dekker]

Thanks for your feedback so far, Brad and Bill,

First of all, I really hope that my proposed fix 
<www.itk.org/Bug/view.php?id=7094> makes sense to you  :-)

Bill Lorensen wrote:
> Is there a technical reason why we
> should not keep the method?

Brad's original ExceptionObject::UpdateWhat() took care of keeping 
m_What up-to-date, whenever other exception data members (m_Description, 
m_Location) were changed.  (m_What contains the text returned by 
what().)  Unfortunately this function could itself not be made exception 
safe: When UpdateWhat() would fail (typically because of a memory 
failure), the text of m_What would no longer correspond to the other 
data members.

My proposed fix would solve this issue (and other issues), by having all 
exception data stored together within an internal, "immutable", 
reference-counted ExceptionData object. Thereby the Set functions would 
become slightly more expensive, because they would have to replace the 
whole ExceptionData at once. But the copy constructor and the assignment 
would become very efficient, and moreover, those functions would become 
non-throwing.  (Because those would just increase the reference 
counter.)

So the ExceptionData object would always be internally consistent, and 
UpdateWhat() wouldn't be necessary anymore.  Of course, we could leave 
it empty. But that wouldn't trigger any /possible/ user to stop calling 
the function.  So maybe this legacy/deprecation scheme could be useful?


Kind regards,

Niels