ofproto: Avoid wasting memory malloc()'ing empty action sets for subrules.

GNU libc treats malloc(0) as malloc(1).  Subrules always have an n_actions
of 0, so this code was wasting time and memory for subrules.  This commit
stops doing that.

Also audits and fixes some very pedantic potential problems with null
pointers; e.g. the C standard says that NULL may not be compared with the
< operator, even if both arguments are null, and it also says that a null
pointer may not be passed to memcpy() or memcmp(), even if the length is
zero.

1 files changed, 5 insertions, 4 deletions

diff --git a/lib/ofp-util.c b/lib/ofp-util.c
index 7a2e17cb2..6d0458673 100644
--- a/lib/ofp-util.c
+++ b/lib/ofp-util.c
@@ -619,9 +619,10 @@ int
 validate_actions(const union ofp_action *actions, size_t n_actions,
                  int max_ports)
 {
-    const union ofp_action *a;
+    size_t i;
 
-    for (a = actions; a < &actions[n_actions]; ) {
+    for (i = 0; i < n_actions; ) {
+        const union ofp_action *a = &actions[i];
         unsigned int len = ntohs(a->header.len);
         unsigned int n_slots = len / ACTION_ALIGNMENT;
         unsigned int slots_left = &actions[n_actions] - a;
@@ -645,7 +646,7 @@ validate_actions(const union ofp_action *actions, size_t n_actions,
         if (error) {
             return error;
         }
-        a += n_slots;
+        i += n_slots;
     }
     return 0;
 }
@@ -679,7 +680,7 @@ actions_first(struct actions_iterator *iter,
 const union ofp_action *
 actions_next(struct actions_iterator *iter)
 {
-    if (iter->pos < iter->end) {
+    if (iter->pos != iter->end) {
         const union ofp_action *a = iter->pos;
         unsigned int len = ntohs(a->header.len);
         iter->pos += len / ACTION_ALIGNMENT;