Summary

ATL provides a rich set of classes for manipulating the data types COM programmers frequently use. The CComVariant class provides practically the same benefits as the CComBSTR class, but for VARIANT structures. If you use a VARIANT structureand you will need to use one sooner or lateryou should instead use the ATL CComVariant smart VARIANT class. You'll have far fewer problems with resource leaks.

SAFEARRAYs have a number of specialized semantics as well. CComSafeArray was shown to be a useful template class for managing both single- and multidimensional SAFEARRAYs. As with other managed resources, however, take care when dealing with CComSafeArray because the compiler cannot always tell you if you've written code that will result in a memory leak.

The CComPtr, CComQIPtr, and CComGITPtr smart pointer classes ease, but do not totally alleviate, the resource management needed for interface pointers. These classes have numerous useful methods that let you write more application code and deal less with the low-level resource-management details. You'll find smart pointers most useful when you're using interface pointers with exception handling.

Finally, you can control memory management in ATL with IAtlMemMgr and five concrete implementations that are supplied: CWin32Heap, CComHeap, CCRTHeap, CLocalHeap, and CGlobalHeap. You can program ATL classes such as CString to use memory from these heaps or even from a custom implementation of IAtlMemMgr, to provide a high degree of control and facilitate any number of performance optimizations.