New upstream version 2.3.4
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556 changed files with 90432 additions and 53391 deletions
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gl/fflush.c
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gl/fflush.c
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/* fflush.c -- allow flushing input streams
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Copyright (C) 2007-2023 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Eric Blake. */
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#include <config.h>
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/* Specification. */
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#include <stdio.h>
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#include <errno.h>
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#include <unistd.h>
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#include "freading.h"
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#include "stdio-impl.h"
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#undef fflush
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#if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
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/* GNU libc, BeOS, Haiku, Linux libc5 */
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/* Clear the stream's ungetc buffer, preserving the value of ftello (fp). */
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static void
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clear_ungetc_buffer_preserving_position (FILE *fp)
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{
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if (fp->_flags & _IO_IN_BACKUP)
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/* _IO_free_backup_area is a bit complicated. Simply call fseek. */
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fseeko (fp, 0, SEEK_CUR);
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}
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#else
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/* Clear the stream's ungetc buffer. May modify the value of ftello (fp). */
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static void
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clear_ungetc_buffer (FILE *fp)
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{
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# if defined __sferror || defined __DragonFly__ || defined __ANDROID__
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/* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
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if (HASUB (fp))
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{
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fp_->_p += fp_->_r;
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fp_->_r = 0;
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}
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# elif defined __EMX__ /* emx+gcc */
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if (fp->_ungetc_count > 0)
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{
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fp->_ungetc_count = 0;
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fp->_rcount = - fp->_rcount;
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}
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# elif defined _IOERR /* Minix, AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, UnixWare, mingw, MSVC, NonStop Kernel, OpenVMS */
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/* Nothing to do. */
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# else /* other implementations */
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fseeko (fp, 0, SEEK_CUR);
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# endif
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}
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#endif
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#if ! (defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1)
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/* GNU libc, BeOS, Haiku, Linux libc5 */
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# if (defined __sferror || defined __DragonFly__ || defined __ANDROID__) && defined __SNPT
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/* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
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static int
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disable_seek_optimization (FILE *fp)
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{
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int saved_flags = fp_->_flags & (__SOPT | __SNPT);
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fp_->_flags = (fp_->_flags & ~__SOPT) | __SNPT;
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return saved_flags;
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}
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static void
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restore_seek_optimization (FILE *fp, int saved_flags)
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{
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fp_->_flags = (fp_->_flags & ~(__SOPT | __SNPT)) | saved_flags;
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}
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# else
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static void
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update_fpos_cache (_GL_ATTRIBUTE_MAYBE_UNUSED FILE *fp,
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_GL_ATTRIBUTE_MAYBE_UNUSED off_t pos)
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{
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# if defined __sferror || defined __DragonFly__ || defined __ANDROID__
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/* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
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# if defined __CYGWIN__ || defined __ANDROID__
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/* fp_->_offset is typed as an integer. */
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fp_->_offset = pos;
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# else
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/* fp_->_offset is an fpos_t. */
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/* Use a union, since on NetBSD, the compilation flags determine
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whether fpos_t is typedef'd to off_t or a struct containing a
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single off_t member. */
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union
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{
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fpos_t f;
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off_t o;
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} u;
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u.o = pos;
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fp_->_offset = u.f;
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# endif
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fp_->_flags |= __SOFF;
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# endif
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}
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# endif
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#endif
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/* Flush all pending data on STREAM according to POSIX rules. Both
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output and seekable input streams are supported. */
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int
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rpl_fflush (FILE *stream)
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{
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/* When stream is NULL, POSIX and C99 only require flushing of "output
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streams and update streams in which the most recent operation was not
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input", and all implementations do this.
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When stream is "an output stream or an update stream in which the most
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recent operation was not input", POSIX and C99 requires that fflush
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writes out any buffered data, and all implementations do this.
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When stream is, however, an input stream or an update stream in
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which the most recent operation was input, C99 specifies nothing,
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and POSIX only specifies behavior if the stream is seekable.
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mingw, in particular, drops the input buffer, leaving the file
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descriptor positioned at the end of the input buffer. I.e. ftell
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(stream) is lost. We don't want to call the implementation's
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fflush in this case.
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We test ! freading (stream) here, rather than fwriting (stream), because
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what we need to know is whether the stream holds a "read buffer", and on
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mingw this is indicated by _IOREAD, regardless of _IOWRT. */
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if (stream == NULL || ! freading (stream))
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return fflush (stream);
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#if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
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/* GNU libc, BeOS, Haiku, Linux libc5 */
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clear_ungetc_buffer_preserving_position (stream);
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return fflush (stream);
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#else
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{
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/* What POSIX says:
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1) About the file-position indicator (-> fseeko, ftello):
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The file position indicator is incremented by fgetc() and decremented
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by ungetc():
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<https://pubs.opengroup.org/onlinepubs/9699919799/functions/fgetc.html>
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"... the fgetc() function shall ... advance the associated file
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position indicator for the stream ..."
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<https://pubs.opengroup.org/onlinepubs/9699919799/functions/ungetc.html>
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"The file-position indicator is decremented by each successful
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call to ungetc()..."
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2) fflush discards bytes pushed back by ungetc:
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<https://pubs.opengroup.org/onlinepubs/9699919799/functions/fflush.html>
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"...any characters pushed back onto the stream by ungetc()
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or ungetwc() that have not subsequently been read from the
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stream shall be discarded..."
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This implies implicitly: fflush does not change the file position
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indicator.
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3) Effects on the file descriptor, if the file descriptor is capable of
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seeking:
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<https://pubs.opengroup.org/onlinepubs/9699919799/functions/fflush.html>
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"...the file offset of the underlying open file description shall
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be set to the file position of the stream..." */
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/* POSIX does not specify fflush behavior for non-seekable input
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streams. Some implementations purge unread data, some return
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EBADF, some do nothing. */
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off_t pos = ftello (stream);
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if (pos == -1)
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{
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errno = EBADF;
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return EOF;
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}
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/* Clear the ungetc buffer. */
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clear_ungetc_buffer (stream);
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/* To get here, we must be flushing a seekable input stream, so the
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semantics of fpurge are now appropriate to clear the buffer. To
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avoid losing data, the lseek is also necessary. */
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{
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int result = fpurge (stream);
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if (result != 0)
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return result;
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}
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# if (defined __sferror || defined __DragonFly__ || defined __ANDROID__) && defined __SNPT
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/* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
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{
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/* Disable seek optimization for the next fseeko call. This tells the
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following fseeko call to seek to the desired position directly, rather
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than to seek to a block-aligned boundary. */
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int saved_flags = disable_seek_optimization (stream);
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int result = fseeko (stream, pos, SEEK_SET);
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restore_seek_optimization (stream, saved_flags);
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return result;
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}
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# else
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pos = lseek (fileno (stream), pos, SEEK_SET);
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if (pos == -1)
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return EOF;
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/* After a successful lseek, update the file descriptor's position cache
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in the stream. */
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update_fpos_cache (stream, pos);
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return 0;
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# endif
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}
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#endif
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}
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