lseek/llseek allows the negative offset

["H . J . Lu" <hjl@valinux.com>]

# gcc x.c
# ./a.out
lseek on -100000: -100000
write: File too large

Should kernel allow negative offsets for lseek/llseek?


-- 
H.J. Lu (hjl@valinux.com)
---
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>

extern loff_t llseek (int fd, loff_t offset, int whence);

int
main ()
{
  int fd = open ("/tmp/foo.out", O_CREAT | O_RDWR, 0600);
  off_t res, pos;
  loff_t lres, lpos;
  char buffer [] = "negative offset";

  if (fd < 0)
    {
      perror ("open");
      return 1;
    }

  pos = -100000;
  res = lseek (fd, pos, SEEK_SET);
  if (res == (off_t) -1L)
    {
      perror ("lseek");
      close (fd);
      return 1;
    }
  printf ("lseek on %ld: %ld\n", pos, res);

  if (write (fd, buffer, sizeof (buffer)) != sizeof (buffer))
    {
      perror ("write");
      close (fd);
      return 1;
    }

  lpos = -100000LL;
  lres = llseek (fd, lpos, SEEK_SET);
  if (lres == (loff_t) -1L)
    {
      perror ("llseek");
      close (fd);
      return 1;
    }

  
  printf ("llseek on %lld: %lld\n", lpos, lres);

  if (write (fd, buffer, sizeof (buffer)) != sizeof (buffer))
    {
      perror ("write");
      close (fd);
      return 1;
    }

  close (fd);

  return 0;
}
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