[vtk-developers] vtkDataArrayTemplate.cxx writes out of bounds when malloc fails

[Burlen Loring]

Hi all,

I would like to get some feed back on a change I would like to make to 
vtkDataArrayTemplate.txx.

Here is the problem that prompted the changes:

Currently during inserts, a data array resizes itself if need be. 
Unfortunately, in the case that it runs out of memory during the resize, 
it ignores the fact that it didn't get the needed space and writes into 
memory it doesn't own. For example take a look at how GetWritePointer is 
ignoring the return value from ResizeAndExtend which, will be 0 to 
indicate that malloc failed. And further how InsertNextTuple/InsertTuple 
has no way of knowing if the malloc failed. The insert then takes place 
into memory not owned by the data array.

If you are unfortunate enough to use enough ram that malloc fails during 
a series of inserts, this can cause some very strange crashes!

Attached is a patch I'd like to submit to cvs. What I have done is 
replace the malloc/free pairs with new/delete pairs. Failure of new is 
much easier to deal with (compared to malloc) because it throws a 
bad_alloc exception, which clearly indicates the nature of the problem, 
and the end user can decide how to handle that.  Additionally the patch 
makes sure that if new returns 0 rather than throwing an exception(could 
happen on older compilers), a return value indicating an error occurred 
gets propagated back up to the caller immediately. For methods that 
return pointers the error value is 0 for methods that return vtkIdType 
the error value is -1. There are a few methods (eg SetTuple) that are 
typed as returning void, which simply return. In the case of new 
failures during an insert, this prevents the data array from writing 
into memory it doesn't own.

Any objections/criticism/comments regarding this change?

Thanks in advance
Burlen

-- 
Burlen Loring
Kitware, Inc.
R&D Engineer
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-371-3971 x137

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