Some debug functions set all the memory they allocate to a specified fill pattern. This lets you easily locate areas in memory that your program uses.
The debug_malloc, debug_realloc, and debug_umalloc functions set allocated memory to a default repeating 0xAA fill pattern. To enable this fill pattern, export the HD_FILL environment variable.
The debug_free function sets all free memory to a repeating 0xFB fill pattern.