Date: Wed, 11 Oct 2006 13:02:28 GMT From: trasz<trasz@pin.if.uz.zgora.p> To: freebsd-gnats-submit@FreeBSD.org Subject: bin/104295: freopen(NULL, ...) does bad things to file offset. Message-ID: <200610111302.k9BD2SbI024342@www.freebsd.org> Resent-Message-ID: <200610111310.k9BDAHFI060386@freefall.freebsd.org>
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>Number: 104295
>Category: bin
>Synopsis: freopen(NULL, ...) does bad things to file offset.
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Oct 11 13:10:17 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator: trasz
>Release: 6.1
>Organization:
>Environment:
FreeBSD traszkan.ds7 6.2-PRERELEASE FreeBSD 6.2-PRERELEASE #1: Fri Sep 29 12:04:37 CEST 2006 trasz@traszkan.ds7:/usr/obj/usr/src/sys/TRASHCAN i386
>Description:
Freopen(3) does bad things to the file offset when supplied with NULL
as a file path (freopen(NULL, mode, fd);). The test program below returns:
file offset before freopen is 100.
file offset after freopen is 2399.
>How-To-Repeat:
#include <stdio.h>
int main(void)
{
int ret;
FILE *f;
f=fopen("/etc/passwd", "r");
if (f==NULL) {
perror("fopen");
exit(-1);
}
ret=fseek(f, 100, SEEK_CUR);
if (ret<0) {
perror("fseek");
exit(-1);
}
ret=ftell(f);
fprintf(stderr, "file offset before freopen is %d.\n", ret);
f=freopen(NULL, "r", f);
if (f==NULL) {
perror("freopen");
exit(-1);
}
ret=ftell(f);
fprintf(stderr, "file offset after freopen is %d.\n", ret);
return 0;
}
>Fix:
NOT TESTED:
--- freopen.c.orig Wed Oct 11 14:59:25 2006
+++ freopen.c Wed Oct 11 15:00:47 2006
@@ -217,5 +217,9 @@
fp->_seek = __sseek;
fp->_close = __sclose;
FUNLOCKFILE(fp);
+
+ if (file == NULL)
+ rewind(fp);
+
return (fp);
}
>Release-Note:
>Audit-Trail:
>Unformatted:
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