Date: Mon, 5 Jul 1999 17:02:59 -0700 (PDT) From: kientzle@acm.org To: freebsd-gnats-submit@freebsd.org Subject: misc/12526: fseek(f,o,SEEK_CUR) broken on large files Message-ID: <19990706000259.E6B0B15001@hub.freebsd.org>
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>Number: 12526
>Category: misc
>Synopsis: fseek(f,o,SEEK_CUR) broken on large files
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Mon Jul 5 17:10:00 PDT 1999
>Closed-Date:
>Last-Modified:
>Originator: Tim Kientzle
>Release: FreeBSD 3.1-RELEASE i386
>Organization:
Independent software consultant
>Environment:
FreeBSD clover.kientzle.com 3.1-RELEASE FreeBSD 3.1-RELEASE #10: Thu Jul 1 13:48:43 PDT 1999 root@clover.kientzle.com:/usr/src/sys/compile/CLOVER i386
>Description:
fseek() does not properly handle SEEK_CUR if the resulting
file position would exceed 2^31.
(Remember that SEEK_CUR and SEEK_END can both be used to seek
beyond 2^31 even though fseek only accepts a 32-bit signed long offset.)
>How-To-Repeat:
In a 4gig file, perform:
fseek(f,0x7fffffffL, SEEK_SET);
fseek(f,0x7fffffffL, SEEK_CUR); /* This seek silently fails */
>Fix:
fseek() correctly uses 64-bit fpos_t arithmetic to compute the new
file offset when converting SEEK_CUR to SEEK_SET, but then assigns the
64-bit result into the 32-bit 'offset' variable.
This can be fixed by changing the variable 'offset' to a 64-bit fpos_t
type, which in turn requires renaming the actual argument to maintain
the ANSI-dictated interface. The three lines marked 'TBKK' below are
the necessary changes.
/usr/src/lib/libc/stdio/fseek.c:
int
fseek(fp, offset32, whence) /* TBKK: renamed 'offset' to 'offset32' */
register FILE *fp;
long offset32; /* TBKK: renamed 'offset' to 'offset32' */
int whence;
{
register fpos_t (*seekfn) __P((void *, fpos_t, int));
fpos_t target, curoff;
fpos_t offset = offset32; /* TBKK: added 64-bit offset variable */
>Release-Note:
>Audit-Trail:
>Unformatted:
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