Hi,
For an fprintf emulation, one needs the ability to set the "error indicator"
bit in a FILE stream. Surprisingly, this is not possible in a portable and
efficient way. Like __fpending, this is one of those functionalities that
the ANSI/ISO C people forgot to standardize.
2007-03-08 Bruno Haible <[EMAIL PROTECTED]>
* modules/fseterr: New file.
* lib/fseterr.h: New file.
* lib/fseterr.c: New file.
============================== modules/fseterr ==============================
Description:
Set the error indicator of a stream.
Files:
lib/fseterr.h
lib/fseterr.c
Depends-on:
configure.ac:
Makefile.am:
lib_SOURCES += fseterr.c
Include:
"fseterr.h"
License:
LGPL
Maintainer:
Bruno Haible
=============================== lib/fseterr.h ===============================
/* Set the error indicator of a stream.
Copyright (C) 2007 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
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, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
#ifndef _FSETERR_H
#define _FSETERR_H
#include <stdio.h>
#ifdef __cplusplus
extern "C" {
#endif
/* Set the error indicator of the stream FP.
The "error indicator" is set when an I/O operation on the stream fails, and
is cleared (together with the "end-of-file" indicator) by clearerr (FP). */
extern void fseterr (FILE *fp);
#ifdef __cplusplus
}
#endif
#endif /* _FSETERR_H */
=============================== lib/fseterr.c ===============================
/* Set the error indicator of a stream.
Copyright (C) 2007 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
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, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
#include <config.h>
/* Specification. */
#include "fseterr.h"
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_ferror_unlocked /* GNU libc, BeOS */
fp->_flags |= _IO_ERR_SEEN;
#elif defined __sferror /* FreeBSD, NetBSD, OpenBSD, MacOS X,
Cygwin */
fp->_flags |= __SERR;
#elif defined _IOERR /* AIX, HP-UX, IRIX, OSF/1, Solaris, mingw
*/
fp->_flag |= _IOERR;
#else /* unknown */
/* Portable fallback, based on an idea by Rich Felker.
Wow! 6 system calls for something that is just a bit operation! */
int fd;
int fd2;
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);
}
#endif
}
