curs_memleaks.3x man page
_nc_freeall _nc_free_and_exit — curses memory-leak checking
These functions are used to simplify analysis of memory leaks in the ncurses library. They are normally not available; they must be configured into the library at build time using the --disable-leaks option. That compiles-in code that frees memory that normally would not be freed.
Any implementation of curses must not free the memory associated with a screen, since (even after calling endwin), it must be available for use in the next call to refresh(3X). There are also chunks of memory held for performance reasons. That makes it hard to analyze curses applications for memory leaks. To work around this, one can build a debugging version of the ncurses library which frees those chunks which it can, and provides these functions to free all of the memory allocated by the ncurses library.
The _nc_free_and_exit function is the preferred one since some of the memory which is freed may be required for the application to continue running. Its parameter is the code to pass to the exit routine.
These functions do not return a value.
These functions are not part of the XSI interface.