[src/trunk]: src/sys/dev Initialize error also in the case where len=0, which...

[maya <maya%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3ba2391f1aa2
branches:  trunk
changeset: 826257:3ba2391f1aa2
user:      maya <maya%NetBSD.org@localhost>
date:      Thu Aug 24 11:26:32 2017 +0000

description:
Initialize error also in the case where len=0, which just succeeds.
while here, assert that the len is indeed non-negative. this is already
confirmed by sys_fdiscard, but let's be sure.

reported by: GCC, but with different compile flags

diffstat:

 sys/dev/dksubr.c |  9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diffs (30 lines):

diff -r 838c7ba682c8 -r 3ba2391f1aa2 sys/dev/dksubr.c
--- a/sys/dev/dksubr.c  Thu Aug 24 10:43:42 2017 +0000
+++ b/sys/dev/dksubr.c  Thu Aug 24 11:26:32 2017 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: dksubr.c,v 1.98 2017/08/13 22:23:16 mlelstv Exp $ */
+/* $NetBSD: dksubr.c,v 1.99 2017/08/24 11:26:32 maya Exp $ */
 
 /*-
  * Copyright (c) 1996, 1997, 1998, 1999, 2002, 2008 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: dksubr.c,v 1.98 2017/08/13 22:23:16 mlelstv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: dksubr.c,v 1.99 2017/08/24 11:26:32 maya Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -497,7 +497,10 @@
        const struct dkdriver *dkd = dksc->sc_dkdev.dk_driver;
        unsigned secsize = dksc->sc_dkdev.dk_geom.dg_secsize;
        struct buf tmp, *bp = &tmp;
-       int maxsz, error;
+       int maxsz;
+       int error = 0;
+
+       KASSERT(len >= 0);
 
        DPRINTF_FOLLOW(("%s(%s, %p, 0x"PRIx64", %jd, %jd)\n", __func__,
            dksc->sc_xname, dksc, (intmax_t)pos, (intmax_t)len));