A complicated task when programming with languages which do not use garbage collected dynamic memory allocation is to find memory leaks. Long running programs must ensure that dynamically allocated objects are freed at the end of their lifetime. If this does not happen the system runs out of memory, sooner or later.
The malloc implementation in the GNU C Library provides some
simple means to detect such leaks and obtain some information to find
the location. To do this the application must be started in a special
mode which is enabled by an environment variable. There are no speed
penalties for the program if the debugging mode is not enabled.