PVS-Studio warning V505 for Crystalspace

#define CS_ALLOC_STACK_ARRAY(type, var, size) \
  type *var = (type *)alloca ((size) * sizeof (type))

void Scene::PropagateLight (....)
{
  ...
  PortalRefArray::Iterator it =
    sourceSector->allPortals.GetIterator ();
  while (it.HasNext ())
  {
    ...
    CS_ALLOC_STACK_ARRAY(csVector3,
      tmpVertices, portal->worldVertices.GetSize ());
    ...
  }
}

This suspicious code was found in Crystalspace project by PVS-Studio static code analyzer.
Warning message is:
V505 The 'alloca' function is used inside the loop. This can quickly overflow stack.  applighter2  scene.cpp  942

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/