[Bug libc/12724] New: fclose violates POSIX 2008 on seekable input streams

["eblake at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=12724

           Summary: fclose violates POSIX 2008 on seekable input streams
           Product: glibc
           Version: 2.13
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper.fsp@gmail.com
        ReportedBy: eblake@redhat.com


POSIX 2008 states:

"If the file is not already at EOF, and the file is one capable of seeking, the
file offset of the underlying open file description shall be adjusted so that
the next operation on the open file description deals with the byte after the
last one read from or written to the stream being closed."

[XSH fclose,
http://pubs.opengroup.org/onlinepubs/9699919799/functions/fclose.html]

However, this sample program proves that for seekable input streams, glibc is
violating this requirement.  The same program runs to completion on Solaris 10.


#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <assert.h>

#define NAME "test-fclose.t"

int
main (void)
{
  const char buf[] = "hello world";
  int fd;
  int fd2;
  FILE *f;

  /* Prepare a seekable file.  */
  fd = open (NAME, O_RDWR | O_CREAT | O_TRUNC, 0600);
  assert (0 <= fd);
  assert (write (fd, buf, sizeof buf) == sizeof buf);
  assert (lseek (fd, 1, SEEK_SET) == 1);

  /* Create an output stream visiting the file; when it is closed, all
     other file descriptors visiting the file must see the new file
     position.  */
  fd2 = dup (fd);
  assert (0 <= fd2);
  f = fdopen (fd2, "w");
  assert (f);
  assert (fputc (buf[1], f) == buf[1]);
  assert (fclose (f) == 0);
  errno = 0;
  assert (lseek (fd2, 0, SEEK_CUR) == -1);
  assert (errno == EBADF);
  assert (lseek (fd, 0, SEEK_CUR) == 2);

  /* Likewise for an input stream.  */
  fd2 = dup (fd);
  assert (0 <= fd2);
  f = fdopen (fd2, "r");
  assert (f);
  assert (fgetc (f) == buf[2]);
  assert (fclose (f) == 0);
  errno = 0;
  assert (lseek (fd2, 0, SEEK_CUR) == -1);
  assert (errno == EBADF);
  assert (lseek (fd, 0, SEEK_CUR) == 3);

  /* Clean up.  */
  assert (remove (NAME) == 0);

  return 0;
}

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.