File: fseterr.c

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/* Set the error indicator of a stream.
   Copyright (C) 2007-2018 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or
   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at your
       option) any later version.

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at your
       option) any later version.

   or both in parallel, as here.
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include "fseterr.h"

#include <errno.h>

#include "stdio-impl.h"

/* This file is not used on systems that have the __fseterr function,
   namely musl libc.  */

void
fseterr (FILE *fp)
{
  /* Most systems provide FILE as a struct and the necessary bitmask in
     <stdio.h>, because they need it for implementing getc() and putc() as
     fast macros.  */
#if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
  /* GNU libc, BeOS, Haiku, Linux libc5 */
  fp->_flags |= _IO_ERR_SEEN;
#elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
  /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
  fp_->_flags |= __SERR;
#elif defined __EMX__               /* emx+gcc */
  fp->_flags |= _IOERR;
#elif defined __minix               /* Minix */
  fp->_flags |= _IOERR;
#elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, MSVC, NonStop Kernel, OpenVMS */
  fp_->_flag |= _IOERR;
#elif defined __UCLIBC__            /* uClibc */
  fp->__modeflags |= __FLAG_ERROR;
#elif defined __QNX__               /* QNX */
  fp->_Mode |= 0x200 /* _MERR */;
#elif defined __MINT__              /* Atari FreeMiNT */
  fp->__error = 1;
#elif defined EPLAN9                /* Plan9 */
  if (fp->state != 0 /* CLOSED */)
    fp->state = 5 /* ERR */;
#elif 0                             /* unknown  */
  /* Portable fallback, based on an idea by Rich Felker.
     Wow! 6 system calls for something that is just a bit operation!
     Not activated on any system, because there is no way to repair FP when
     the sequence of system calls fails, and library code should not call
     abort().  */
  int saved_errno;
  int fd;
  int fd2;

  saved_errno = errno;
  fflush (fp);
  fd = fileno (fp);
  fd2 = dup (fd);
  if (fd2 >= 0)
    {
      close (fd);
      fputc ('\0', fp); /* This should set the error indicator.  */
      fflush (fp);      /* Or this.  */
      if (dup2 (fd2, fd) < 0)
        /* Whee... we botched the stream and now cannot restore it!  */
        abort ();
      close (fd2);
    }
  errno = saved_errno;
#else
 #error "Please port gnulib fseterr.c to your platform! Look at the definitions of ferror and clearerr on your system, then report this to bug-gnulib."
#endif
}