This variable instructs the runtime SORT routine to use the system qsort() function, rather than the built-in sort function. Set USE_SYSTEM_QSORT to 1 if you want to use the system qsort() function. The default value is 0 and results in the use of the built-in sort function.

Some systems have qsort() functions that perform better than the built-in function. Consider experimenting with this variable's settings to determine if this option yields better performance on your system. Pay particular attention to the number of comparisons done during the sort, which can be seen in the runtime trace output.