[src/trunk]: src/sys/netinet6 Initialize variable used as (conditional) resul...

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

details:   https://anonhg.NetBSD.org/src/rev/588bc1246d98
branches:  trunk
changeset: 785537:588bc1246d98
user:      gdt <gdt%NetBSD.org@localhost>
date:      Mon Mar 18 19:31:39 2013 +0000

description:
Initialize variable used as (conditional) result parameter.

ip6_insertfraghdr either sets a result parameter or returns an error.
While the caller only uses the result parameter in the non-error case,
knowing that requires cross-module static analysis, and that's not
robust against distant code changes.  Therfore, set ip6f to NULL
before the function call that maybe sets it, avoiding a spuruious
warning and changing the future possible bug from an unitialized
dereference to a NULL deferrence.

diffstat:

 sys/netinet6/ip6_output.c |  9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diffs (30 lines):

diff -r 43f66aab2064 -r 588bc1246d98 sys/netinet6/ip6_output.c
--- a/sys/netinet6/ip6_output.c Mon Mar 18 16:32:32 2013 +0000
+++ b/sys/netinet6/ip6_output.c Mon Mar 18 19:31:39 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ip6_output.c,v 1.151 2013/01/25 10:33:53 kefren Exp $  */
+/*     $NetBSD: ip6_output.c,v 1.152 2013/03/18 19:31:39 gdt Exp $     */
 /*     $KAME: ip6_output.c,v 1.172 2001/03/25 09:55:56 itojun Exp $    */
 
 /*
@@ -62,7 +62,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ip6_output.c,v 1.151 2013/01/25 10:33:53 kefren Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ip6_output.c,v 1.152 2013/03/18 19:31:39 gdt Exp $");
 
 #include "opt_inet.h"
 #include "opt_inet6.h"
@@ -905,6 +905,11 @@
                        mhip6 = mtod(m, struct ip6_hdr *);
                        *mhip6 = *ip6;
                        m->m_len = sizeof(*mhip6);
+                       /*
+                        * ip6f must be valid if error is 0.  But how
+                        * can a compiler be expected to infer this?
+                        */
+                       ip6f = NULL;
                        error = ip6_insertfraghdr(m0, m, hlen, &ip6f);
                        if (error) {
                                IP6_STATINC(IP6_STAT_ODROPPED);