The short answer: Someone, somewhere, has created a random file entitled "time.h". Your include path has included the directory this is in. This is short-circuiting the system in a non-obvious way. The file doesn't even have to be used, it could be a random test scratch file that one of the programmers put together on the side, not incorporated in. It simply has to exist, and be reachable in your greater include path. This will be enough to hose you. Not a FLTK problem at all.
The longer answer: stat.h
got upgraded from based on __time_t st_atime
etc. to being based on struct timespec st_atim
etc. [note missing e on end] for handling nanosecond resolution timestamps. But timespec is defined in the system's time.h
. If you include a random time.h somewhere in your path, this shadows the include, wiping out the definition of struct timespec.
Apparently this same issue is also a problem with FFMpeg v1.0 and /include/libavutil.
Bottom line: Insist no one ever makes a file called "time.h".