lib/46501: Failure in fpurge.

[henning.petersen%t-online.de@localhost]

>Number:         46501
>Category:       lib
>Synopsis:       Failure in fpurge.
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed May 30 11:00:00 +0000 2012
>Originator:     Henning Petersen
>Release:        NetBSD-current
>Organization:
>Environment:
>Description:
Test programm is writing "abc" in file "bar", it should be "abcd".
With the patch taken from FreeBSD it is correct.
>How-To-Repeat:
With this test I got "abc".

#include <stdio.h>
#include <stdlib.h>

int main (int argc, char **argv)
{
FILE *f = fopen("bar", "w+");
fputs ("abc", f);
rewind (f);
while (EOF != fgetc (f));
fpurge (f);
argc > 1 ? putc ('d', f) : fputc ('d', f);
return 0;
}

>Fix:
diff -u -p -r1.14 fpurge.c
--- lib/libc/stdio/fpurge.c     15 Mar 2012 18:22:30 -0000      1.14
+++ lib/libc/stdio/fpurge.c     30 May 2012 09:06:57 -0000
@@ -69,7 +69,7 @@ fpurge(FILE *fp)
        WCIO_FREE(fp);
        fp->_p = fp->_bf._base;
        fp->_r = 0;
-       fp->_w = fp->_flags & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
+       fp->_w = fp->_flags & (__SLBF|__SNBF|__SRD) ? 0 : fp->_bf._size;
        FUNLOCKFILE(fp);
        return 0;
 }