assertion "ptr != MAP_FAILED" failed while using mmap

["Alex Vinokur" <alexvn at connect dot to>]

===========================================
Windows 2000
CYGWIN_NT-5.0 1.3.22(0.78/3/2)
GNU gcc version 3.2 20020927 (prerelease)
===========================================

Here is some function.

--------------------------------------
void read_file (char* filename_i)
{
int fd = open(filename_i, O_RDONLY);
  assert (fd > 2);

off_t sz = lseek(fd, 0, SEEK_END);
char* ptr = (char*)mmap(0, sz, PROT_READ, 0, fd, 0);

  assert (ptr != MAP_FAILED);  // Here assertion failed
  if (ptr != MAP_FAILED)
  {
    string str(ptr, ptr+sz);
    munmap(ptr, sz);
  }

  close(fd);
}
--------------------------------------

Assertion  "ptr != MAP_FAILED)" failed.
What might cause that?

Thanks,
--
   ==========================================
   Alex Vinokur
     mailto:alexvn@connect.to
     http://www.simtel.net/pub/oth/19088.html
     http://sourceforge.net/users/alexvn
   ==========================================






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