these are linux specific constants. glibc exposes them behind
_GNU_SOURCE, but, since SEEK_* is reserved for the implementation, we
can simply define them. furthermore, since they can't be used with
fseek() and other functions that deal with FILE, we don't add them to
stdio.h.
#define SEEK_SET 0
#define SEEK_CUR 1
#define SEEK_END 2
#define SEEK_SET 0
#define SEEK_CUR 1
#define SEEK_END 2
+#define SEEK_DATA 3
+#define SEEK_HOLE 4
#if __cplusplus >= 201103L
#define NULL nullptr
#if __cplusplus >= 201103L
#define NULL nullptr