Fwd: Re: deleting null pointer arrays (was: Re: extragear/network/ktorrent)

[Michael Pyne]

On Thursday 15 January 2009, Dominik Haumann wrote:
> Hi,
>
> according to [1] this change is wrong:
> >>         BitSet & BitSet::operator = (const BitSet & bs)
> >>         {
> >> -               if (data)
> >> -                       delete [] data;
> >> +               delete [] data
>
> Still, it seems to be unclear whether that's sill an issue.
> Does anyone have an idea?
>
> Dominik
>
> [1]
> http://techbase.kde.org/Development/Tutorials/Common_Programming_Mistakes#N
>ULL_pointer_issues

The way delete [] works is that the size of the array is embedded somewhere in 
the array to be deleted (handled by the corresponding new[]).  delete[] uses 
this information to free the array appropriately.

Apparently the "recent Solaris compiler" does not check for 0 before trying to 
find the hidden array length.

Section 5.3.5 of the C++ standard seems to define what happens when delete is 
called, and says that delete doing nothing for null pointers applies for both 
delete and delete[].  So the Solaris compiler has a bug.

Whether or not we want to work around it is a different story but delete[] on 
a null pointer is perfectly valid C++.

Regards,
 - Michael Pyne
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