I can't think of a single reason in ITK to use alloca. Pretty much every use
case for alloca can be implemented using C++ language features in a more robust
manner.
Maybe it's unfair to say, but I think that the only reason it hasn't fallen out
of use entirely is the esteem in which it is held by certain programmers
associated with the GNU project. That's the one place it crept into VTK -- a
bison-generated parser they've been modifying for years.
The following has been a workaround I've used since C++ hasn't supported
dynamically sized arrays in the past -- I believe it is a gnu extension (that,
by the way, uses alloca under the covers). Of course, in most cases, it is
preferable to use a STL container. I don't remember who said it first but it's
true: Arrays are to data what goto is to code.
It is very nearly as efficient as raw array access, and the actual array is on
the heap:
#include <cstddef>
template <typename TElement>
class DynArray
{
public:
typedef std::size_t size_type;
DynArray(size_type numElements) : m_Size(numElements)
{
this->m_Array = new TElement[numElements];
}
~DynArray()
{
delete [] this->m_Array;
}
TElement &operator[](size_type idx)
{
if(idx > this->m_Size)
{
throw;
}
return this->m_Array[idx];
}
const TElement &operator[](size_type idx) const
{
if(idx > this->m_Size)
{
throw;
}
return this->m_Array[idx];
}
private:
TElement *m_Array;
size_type m_Size;
};
--
Kent Williams [email protected]
On 3/12/13 7:54 AM, "Bradley Lowekamp"
<[email protected]<mailto:[email protected]>> wrote:
Hello,
I am thinking about using the "alloca" function in some code I'm working on for
ITK, and wonder what other people think of it or others experience...
>From the BSD Library Functions Manual:
DESCRIPTION
The alloca() macro allocates size bytes of space in the stack frame of the
caller. This temporary space is automatically freed on return.
I am planning on using it for some dimension sized array in compiled
templateless code, in lieu of C99 dynamic stack based arrays.
Best as I can tell Windows defines it as _alloca, so a little CMake try compile
is going to be needed, not a big deal.
Thanks,
Brad
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
Kitware offers ITK Training Courses, for more information visit:
http://kitware.com/products/protraining.php
Please keep messages on-topic and check the ITK FAQ at:
http://www.itk.org/Wiki/ITK_FAQ
Follow this link to subscribe/unsubscribe:
http://www.itk.org/mailman/listinfo/insight-developers
________________________________
Notice: This UI Health Care e-mail (including attachments) is covered by the
Electronic Communications Privacy Act, 18 U.S.C. 2510-2521, is confidential and
may be legally privileged. If you are not the intended recipient, you are
hereby notified that any retention, dissemination, distribution, or copying of
this communication is strictly prohibited. Please reply to the sender that you
have received the message in error, then delete it. Thank you.
________________________________
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
Kitware offers ITK Training Courses, for more information visit:
http://kitware.com/products/protraining.php
Please keep messages on-topic and check the ITK FAQ at:
http://www.itk.org/Wiki/ITK_FAQ
Follow this link to subscribe/unsubscribe:
http://www.itk.org/mailman/listinfo/insight-developers
