Libc-498.tar.gz

[apple/libc.git] / stdio / FreeBSD / fflush.c

diff --git a/stdio/FreeBSD/fflush.c b/stdio/FreeBSD/fflush.c
index 573241013238279ecd98a061f7b5023a146cb8a0..59da908229eaeb4550acb2a6e575a901c56f1b90 100644 (file)
--- a/stdio/FreeBSD/fflush.c
+++ b/stdio/FreeBSD/fflush.c
@@ -38,7 +38,7 @@
 static char sccsid[] = "@(#)fflush.c   8.1 (Berkeley) 6/4/93";
 #endif /* LIBC_SCCS and not lint */
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD: src/lib/libc/stdio/fflush.c,v 1.12 2002/03/22 21:53:04 obrien Exp $");
+__FBSDID("$FreeBSD: src/lib/libc/stdio/fflush.c,v 1.13 2004/07/04 20:17:00 cperciva Exp $");
 
 #include "namespace.h"
 #include <errno.h>
@@ -61,6 +61,18 @@ fflush(FILE *fp)
        if (fp == NULL)
                return (_fwalk(sflush_locked));
        FLOCKFILE(fp);
+
+       /*
+        * There is disagreement about the correct behaviour of fflush()
+        * when passed a file which is not open for reading.  According to
+        * the ISO C standard, the behaviour is undefined.
+        * Under linux, such an fflush returns success and has no effect;
+        * under Windows, such an fflush is documented as behaving instead
+        * as fpurge().
+        * Given that applications may be written with the expectation of
+        * either of these two behaviours, the only safe (non-astonishing)
+        * option is to return EBADF and ask that applications be fixed.
+        */
        if ((fp->_flags & (__SWR | __SRW)) == 0) {
                errno = EBADF;
                retval = EOF;