The debug version of the Microsoft C run-time library uses the following flags to control the heap allocation and reporting process. For more information, see CRT Debugging Techniques.
Maps the base heap functions to their debug version counterparts
Enables the use of the debugging versions of the run-time functions
Controls how the debug heap manager tracks allocations
These flags can be defined with a /D command-line option or with a #define directive. When the flag is defined with #define, the directive must appear before the header file include statement for the routine declarations.