[Vxl-users] Avoiding problems with smart pointers

[Rob C. <rob...@at...>]

I found out about this the hard way.  You may already be aware of it.  Is
there a way to prevent it?  Maybe by preventing assignment of normal
pointers to smart pointers?

In the following program, the assignment of either aPtr or the address of
aSpatial (depending on the definition of INNER_CRASH) to aSPtr will ref()
that object, increasing its reference count from 0 to 1.  When aSPtr goes
out of scope, its destructor will unref() the object, decreasing its
reference count from 1 to 0.  When this happends, unref() actually deletes
the object.

If INNER_CRASH is defined, this means it will try to delete aSpatial and
crash immediately.  If INNER_CRASH is not defined, it will delete the object
pointed to by aPtr.  The program will then crash as soon as soon as it tries
to acces the object via "aPtr->valid_time(0)".

Rob Campbell

#include <iostream>
#include <vxl/vxl/vcsl/vcsl_spatial.h>

#define INNER_CRASH

int main()
{
	vcsl_spatial aSpatial;
	vcsl_spatial *aPtr = new vcsl_spatial;

	{
		#ifdef INNER_CRASH
			vcsl_spatial_sptr aSPtr = &aSpatial;
		#else
			vcsl_spatial_sptr aSPtr = aPtr;
		#endif
	}
	std::cout << "Outside of inner scope\n";

	aPtr->valid_time(0);

	return 1;
}
Robert J. Campbell Jr.
rob...@at...