An
Objective C preprocessor directive nearly identical to
#include,
except that it
checks to see if the
file has
already been
included.
gcc supports it, but doesn't like it, and will bark a rather large warning to stderr if you use it. Instead, they encourage you to do this in the header:
#ifndef __SOMEFILE_H__
#define __SOMEFILE_H__
...
#endif
-Wno-import gets rid of this
warning.