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According to Paul Eggert on 4/2/2007 12:41 PM:
>
> Anyway, for what it's worth I think fflush (stdin) should behave like
> 1988 POSIX and glibc, at least for apps that care about this sort of
> thing.
Here's my first attempt at this. I don't have easy access to any systems
where fflush(stdin) chokes; should I go ahead and check this in so that
others can help test the module?
2007-04-07 Eric Blake <[EMAIL PROTECTED]>
* lib/stdio_.h [REPLACE_FFLUSH]: Declare rpl_fflush.
* modules/stdio (Makefile.am): Support fflush.
* m4/stdio_h.m4 (gl_STDIO_H_DEFAULTS): Likewise.
* modules/fflush: New file.
* lib/fflush.c: Likewise.
* m4/fflush.m4: Likewise.
* modules/fflush-tests: New test.
* tests/test-fflush.c: Likewise.
* MODULES.html.sh (Input/output <stdio.h>): Document new module.
- --
Don't work too hard, make some time for fun as well!
Eric Blake [EMAIL PROTECTED]
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diff --git a/ChangeLog b/ChangeLog
index e147cff..54113c9 100644
diff --git a/MODULES.html.sh b/MODULES.html.sh
index de3c03d..b8134f3 100755
--- a/MODULES.html.sh
+++ b/MODULES.html.sh
@@ -1543,6 +1543,7 @@ func_all_modules ()
func_echo "$element"
func_begin_table
+ func_module fflush
func_module fseterr
func_module tmpfile
func_end_table
diff --git a/lib/fflush.c b/lib/fflush.c
new file mode 100644
index 0000000..438f257
--- /dev/null
+++ b/lib/fflush.c
@@ -0,0 +1,106 @@
+/* fflush.c -- allow flushing input streams
+ 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. */
+
+/* Written by Eric Blake. */
+
+#include <config.h>
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#if HAVE_STDIO_EXT_H
+# include <stdio_ext.h>
+#endif
+
+#if HAVE_FPURGE && ! HAVE_DECL_FPURGE
+int fpurge (FILE *);
+#endif
+
+#undef fflush
+
+/* Flush all pending data on STREAM according to POSIX rules. Both
+ output and seekable input streams are supported. */
+int
+rpl_fflush (FILE *stream)
+{
+ int e1; /* Leave errno unchanged on success. */
+ int e2; /* Capture errno of first fflush if nothing else succeeds. */
+ int result;
+
+ /* When STREAM is NULL, POSIX only requires flushing of output streams. */
+ if (!stream)
+ return fflush (stream);
+
+ /* Try flushing the stream. C89 guarantees behavior of output
+ streams, so we only need to worry if failure might have been on
+ an input stream. */
+ e1 = errno;
+ result = fflush (stream);
+ if (result == 0 || errno != EBADF)
+ return result;
+
+ /* POSIX does not specify behavior for non-seekable streams. */
+ e2 = errno;
+ if (fseeko (stream, 0, SEEK_CUR) != 0)
+ {
+ errno = e2;
+ return EOF;
+ }
+
+ /* To get here, we must be flushing a seekable input stream, so the
+ semantics of fpurge are now appropriate. */
+#if HAVE_FPURGE
+ errno = e1;
+ result = fpurge (stream);
+#elif HAVE___FPURGE
+ /* __fpurge has no return value, so we must check errno. */
+ errno = 0;
+ __fpurge (stream);
+ if (errno)
+ result = EOF;
+ else
+ {
+ result = 0;
+ errno = e1;
+ }
+#else /* ! HAVE___FPURGE */
+
+ /* No single replacement; do it manually. */
+ {
+ off_t position = ftello (stream);
+ if (position == -1)
+ {
+ result = EOF; /* Should not happen; we know stream is seekable. */
+ }
+ /* Set position of underlying fd first; hopefully we don't confuse
+ the stdio routines. */
+ else if (lseek (fileno (stream), position, SEEK_SET) != position
+ || fseeko (stream, position, SEEK_SET) != 0)
+ {
+ result = EOF;
+ errno = e2;
+ }
+ else
+ {
+ result = 0;
+ errno = e1;
+ }
+ }
+#endif /* ! HAVE___FPURGE */
+
+ return result;
+}
diff --git a/lib/stdio_.h b/lib/stdio_.h
index 183cf7f..08e0252 100644
--- a/lib/stdio_.h
+++ b/lib/stdio_.h
@@ -200,6 +200,13 @@ extern int vsprintf (char *str, const char *format,
va_list args)
# endif
#endif
+#if @GNULIB_FFLUSH@ && @REPLACE_FFLUSH@
+# define fflush rpl_fflush
+ /* Flush all pending data on STREAM according to POSIX rules. Both
+ output and seekable input streams are supported. */
+ extern int fflush (FILE *gl_stream);
+#endif
+
#ifdef __cplusplus
}
#endif
diff --git a/m4/fflush.m4 b/m4/fflush.m4
new file mode 100644
index 0000000..a9889d4
--- /dev/null
+++ b/m4/fflush.m4
@@ -0,0 +1,60 @@
+#serial 1
+
+# Copyright (C) 2007 Free Software Foundation, Inc.
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+dnl From Eric Blake
+
+dnl Find out how to obey POSIX semantics of fflush(stdin) discarding
+dnl unread input, rather than C99 undefined semantics. fpurge is not
+dnl standardized, but has the desired properties.
+
+AC_DEFUN([gl_FUNC_FFLUSH],
+[
+ AC_CACHE_CHECK([whether fflush works on input streams],
+ [gl_cv_func_fflush_stdin],
+ [echo hello world > conftest.txt
+ AC_RUN_IFELSE([AC_LANG_PROGRAM(
+ [[
+#include <stdio.h>
+#include <unistd.h>
+ ]], [[FILE *f = fopen ("conftest.txt", "r");
+ char buffer[10];
+ int fd = fileno (f);
+ if (!f || 0 > fd || fread (buffer, 1, 5, f) != 5)
+ return 2;
+ /* For deterministic results, ensure f read a bigger buffer. */
+ if (lseek (fd, 0, SEEK_CUR) == 5)
+ return 3;
+ /* POSIX requires fflush-fseek to set file offset of fd. */
+ if (fflush (f) != 0 || fseek (f, 0, SEEK_CUR) != 0)
+ return 4;
+ return !(lseek (fd, 0, SEEK_CUR) == 5);
+ ]])], [gl_cv_func_fflush_stdin=yes], [gl_cv_func_fflush_stdin=no],
+ [dnl Pessimistically assume fflush is broken. This is wrong for
+ dnl at least glibc and cygwin; but lib/fflush.c takes this into account.
+ gl_cv_func_fflush_stdin=no])
+ rm conftest.txt
+ ])
+ if test $gl_cv_func_fflush_stdin = no; then
+ gl_REPLACE_FFLUSH
+ fi
+])
+
+AC_DEFUN([gl_REPLACE_FFLUSH],
+[
+ AC_CHECK_HEADERS_ONCE([stdio_ext.h])
+ AC_CHECK_FUNCS_ONCE([fpurge __fpurge])
+dnl Linux documents int fpurge(), but only declares void __fpurge().
+ AC_CHECK_DECLS([fpurge], [], [], [[
+#include <stdio.h>
+#if HAVE_STDIO_EXT_H
+# include <stdio_ext.h>
+#endif
+]])
+ AC_LIBOBJ([fflush])
+ AC_REQUIRE([gl_STDIO_H_DEFAULTS])
+ REPLACE_FFLUSH=1
+])
diff --git a/m4/stdio_h.m4 b/m4/stdio_h.m4
index 5561626..d53997f 100644
--- a/m4/stdio_h.m4
+++ b/m4/stdio_h.m4
@@ -30,6 +30,7 @@ AC_DEFUN([gl_STDIO_H_DEFAULTS],
GNULIB_VSNPRINTF=0; AC_SUBST([GNULIB_VSNPRINTF])
GNULIB_VSPRINTF_POSIX=0; AC_SUBST([GNULIB_VSPRINTF_POSIX])
GNULIB_VASPRINTF=0; AC_SUBST([GNULIB_VASPRINTF])
+ GNULIB_FFLUSH=0; AC_SUBST([GNULIB_FFLUSH])
dnl Assume proper GNU behavior unless another module says otherwise.
REPLACE_FPRINTF=0; AC_SUBST([REPLACE_FPRINTF])
REPLACE_VFPRINTF=0; AC_SUBST([REPLACE_VFPRINTF])
@@ -43,4 +44,5 @@ AC_DEFUN([gl_STDIO_H_DEFAULTS],
REPLACE_VSPRINTF=0; AC_SUBST([REPLACE_VSPRINTF])
HAVE_VASPRINTF=1; AC_SUBST([HAVE_VASPRINTF])
REPLACE_VASPRINTF=0; AC_SUBST([REPLACE_VASPRINTF])
+ REPLACE_FFLUSH=0; AC_SUBST([REPLACE_FFLUSH])
])
diff --git a/modules/fflush b/modules/fflush
new file mode 100644
index 0000000..bee44b1
--- /dev/null
+++ b/modules/fflush
@@ -0,0 +1,24 @@
+Description:
+Discard pending data on both input and output streams.
+
+Files:
+lib/fflush.c
+m4/fflush.m4
+
+Depends-on:
+stdio
+unistd
+
+configure.ac:
+gl_FUNC_FFLUSH
+gl_STDIO_MODULE_INDICATOR([fflush])
+
+Makefile.am:
+
+Include:
+
+License:
+GPL
+
+Maintainer:
+Eric Blake
diff --git a/modules/fflush-tests b/modules/fflush-tests
new file mode 100644
index 0000000..aaec63e
--- /dev/null
+++ b/modules/fflush-tests
@@ -0,0 +1,11 @@
+Files:
+tests/test-fflush.c
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-fflush
+check_PROGRAMS += test-fflush
+EXTRA_DIST += test-fflush.c
diff --git a/modules/stdio b/modules/stdio
index 456e323..3ee2d0b 100644
--- a/modules/stdio
+++ b/modules/stdio
@@ -30,6 +30,7 @@ stdio.h: stdio_.h
-e 's|@''GNULIB_VSNPRINTF''@|$(GNULIB_VSNPRINTF)|g' \
-e 's|@''GNULIB_VSPRINTF_POSIX''@|$(GNULIB_VSPRINTF_POSIX)|g' \
-e 's|@''GNULIB_VASPRINTF''@|$(GNULIB_VASPRINTF)|g' \
+ -e 's|@''GNULIB_FFLUSH''@|$(GNULIB_FFLUSH)|g' \
-e 's|@''REPLACE_FPRINTF''@|$(REPLACE_FPRINTF)|g' \
-e 's|@''REPLACE_VFPRINTF''@|$(REPLACE_VFPRINTF)|g' \
-e 's|@''REPLACE_PRINTF''@|$(REPLACE_PRINTF)|g' \
@@ -42,6 +43,7 @@ stdio.h: stdio_.h
-e 's|@''REPLACE_VSPRINTF''@|$(REPLACE_VSPRINTF)|g' \
-e 's|@''HAVE_VASPRINTF''@|$(HAVE_VASPRINTF)|g' \
-e 's|@''REPLACE_VASPRINTF''@|$(REPLACE_VASPRINTF)|g' \
+ -e 's|@''REPLACE_FFLUSH''@|$(REPLACE_FFLUSH)|g' \
-e '/definition of GL_LINK_WARNING/r $(LINK_WARNING_H)' \
< $(srcdir)/stdio_.h; \
} > [EMAIL PROTECTED]
diff --git a/tests/test-fflush.c b/tests/test-fflush.c
new file mode 100644
index 0000000..276d8bf
--- /dev/null
+++ b/tests/test-fflush.c
@@ -0,0 +1,88 @@
+/* Test of POSIX compatible fflush() function.
+ 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. */
+
+/* Written by Eric Blake, 2007. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <stdio.h>
+#include <unistd.h>
+
+int
+main (int argc, char *argv[])
+{
+ FILE *f;
+ char buffer[10];
+ int fd;
+
+ /* Create test file. */
+ f = fopen ("test-fflush.txt", "w");
+ if (!f || fwrite ("1234567890", 1, 10, f) != 10 || fclose (f) != 0)
+ {
+ fputs ("Failed to create sample file.\n", stderr);
+ unlink ("test-fflush.txt");
+ return 1;
+ }
+
+ /* Test fflush. */
+ f = fopen ("test-fflush.txt", "r");
+ fd = fileno (f);
+ if (!f || 0 > fd || fread (buffer, 1, 5, f) != 5)
+ {
+ fputs ("Failed initial read of sample file.\n", stderr);
+ fclose (f);
+ unlink ("test-fflush.txt");
+ return 1;
+ }
+ /* For deterministic results, ensure f read a bigger buffer. */
+ if (lseek (fd, 0, SEEK_CUR) == 5)
+ {
+ fputs ("Sample file was not buffered.\n", stderr);
+ fclose (f);
+ unlink ("test-fflush.txt");
+ return 1;
+ }
+ /* POSIX requires fflush-fseek to set file offset of fd. */
+ if (fflush (f) != 0 || fseek (f, 0, SEEK_CUR) != 0)
+ {
+ fputs ("Failed to flush sample file.\n", stderr);
+ fclose (f);
+ unlink ("test-fflush.txt");
+ return 1;
+ }
+ /* Check that offset is correct. */
+ if (lseek (fd, 0, SEEK_CUR) != 5)
+ {
+ fputs ("File offset is wrong.\n", stderr);
+ fclose (f);
+ unlink ("test-fflush.txt");
+ return 1;
+ }
+ /* Check that file reading resumes at correct location. */
+ if (fgetc (f) != '6')
+ {
+ fputs ("Failed to read next byte of file.\n", stderr);
+ fclose (f);
+ unlink ("test-fflush.txt");
+ return 1;
+ }
+ fclose (f);
+ unlink ("test-fflush.txt");
+ return 0;
+}
