An FIU message describes file descriptors that are in use by your program.
To generate a list of file descriptors in use, set the option -purify-fds-inuse-at-exit=yes (the default), or the API function purify_new_fds_inuse, or purify_all_fds_inuse.
Each FIU message describes what is known about the origin of one open file descriptor. If you see multiple descriptors for the same file, or from the same call chain in the program, you should be concerned that you have a file descriptor leak, and your program might run out of file descriptors.
For more information about file descriptor leaks, click 