list: use multi-variable helpers for list loops.

Use multi-variable iteration helpers to rewrite non-safe loops.

There is an important behavior change compared with the previous
implementation: When the loop ends normally (i.e: not via "break;"), the
object pointer provided by the user is NULL. This is safer because it's
not guaranteed that it would end up pointing a valid address.

For pop iterator, set the variable to NULL when the loop ends.

Clang-analyzer has successfully picked the potential null-pointer
dereference on the code that triggered this change (bond.c) and nothing
else has been detected.

For _SAFE loops, use the LONG version for backwards compatibility.

Acked-by: Eelco Chaudron <echaudro@redhat.com>
Acked-by: Dumitru Ceara <dceara@redhat.com>
Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

1 files changed, 42 insertions, 31 deletions

diff --git a/include/openvswitch/list.h b/include/openvswitch/list.h
index 8ad5eeb32..bbd2edbd0 100644
--- a/include/openvswitch/list.h
+++ b/include/openvswitch/list.h
@@ -72,37 +72,48 @@ static inline bool ovs_list_is_empty(const struct ovs_list *);
 static inline bool ovs_list_is_singleton(const struct ovs_list *);
 static inline bool ovs_list_is_short(const struct ovs_list *);
 
-#define LIST_FOR_EACH(ITER, MEMBER, LIST)                               \
-    for (INIT_CONTAINER(ITER, (LIST)->next, MEMBER);                    \
-         &(ITER)->MEMBER != (LIST);                                     \
-         ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.next, MEMBER))
-#define LIST_FOR_EACH_CONTINUE(ITER, MEMBER, LIST)                      \
-    for (ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.next, MEMBER);             \
-         &(ITER)->MEMBER != (LIST);                                     \
-         ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.next, MEMBER))
-#define LIST_FOR_EACH_REVERSE(ITER, MEMBER, LIST)                       \
-    for (INIT_CONTAINER(ITER, (LIST)->prev, MEMBER);                    \
-         &(ITER)->MEMBER != (LIST);                                     \
-         ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.prev, MEMBER))
-#define LIST_FOR_EACH_REVERSE_SAFE(ITER, PREV, MEMBER, LIST)        \
-    for (INIT_CONTAINER(ITER, (LIST)->prev, MEMBER);                \
-         (&(ITER)->MEMBER != (LIST)                                 \
-          ? INIT_CONTAINER(PREV, (ITER)->MEMBER.prev, MEMBER), 1    \
-          : 0);                                                     \
-         (ITER) = (PREV))
-#define LIST_FOR_EACH_REVERSE_CONTINUE(ITER, MEMBER, LIST)              \
-    for (ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.prev, MEMBER);           \
-         &(ITER)->MEMBER != (LIST);                                     \
-         ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.prev, MEMBER))
-#define LIST_FOR_EACH_SAFE(ITER, NEXT, MEMBER, LIST)               \
-    for (INIT_CONTAINER(ITER, (LIST)->next, MEMBER);               \
-         (&(ITER)->MEMBER != (LIST)                                \
-          ? INIT_CONTAINER(NEXT, (ITER)->MEMBER.next, MEMBER), 1   \
-          : 0);                                                    \
-         (ITER) = (NEXT))
-#define LIST_FOR_EACH_POP(ITER, MEMBER, LIST)                      \
-    while (!ovs_list_is_empty(LIST)                                    \
-           && (INIT_CONTAINER(ITER, ovs_list_pop_front(LIST), MEMBER), 1))
+#define LIST_FOR_EACH(VAR, MEMBER, LIST)                                      \
+    for (INIT_MULTIVAR(VAR, MEMBER, (LIST)->next, struct ovs_list);           \
+         CONDITION_MULTIVAR(VAR, MEMBER, ITER_VAR(VAR) != (LIST));            \
+         UPDATE_MULTIVAR(VAR, ITER_VAR(VAR)->next))
+
+#define LIST_FOR_EACH_CONTINUE(VAR, MEMBER, LIST)                             \
+    for (INIT_MULTIVAR(VAR, MEMBER, VAR->MEMBER.next, struct ovs_list);       \
+         CONDITION_MULTIVAR(VAR, MEMBER, ITER_VAR(VAR) != (LIST));            \
+         UPDATE_MULTIVAR(VAR, ITER_VAR(VAR)->next))
+
+#define LIST_FOR_EACH_REVERSE(VAR, MEMBER, LIST)                              \
+    for (INIT_MULTIVAR(VAR, MEMBER, (LIST)->prev, struct ovs_list);           \
+         CONDITION_MULTIVAR(VAR, MEMBER, ITER_VAR(VAR) != (LIST));            \
+         UPDATE_MULTIVAR(VAR, ITER_VAR(VAR)->prev))
+
+#define LIST_FOR_EACH_REVERSE_CONTINUE(VAR, MEMBER, LIST)                     \
+    for (INIT_MULTIVAR(VAR, MEMBER, VAR->MEMBER.prev, struct ovs_list);       \
+         CONDITION_MULTIVAR(VAR, MEMBER, ITER_VAR(VAR) != (LIST));            \
+         UPDATE_MULTIVAR(VAR, ITER_VAR(VAR)->prev))
+
+#define LIST_FOR_EACH_REVERSE_SAFE(VAR, PREV, MEMBER, LIST)                   \
+    for (INIT_MULTIVAR_SAFE_LONG(VAR, PREV, MEMBER, (LIST)->prev,             \
+                                 struct ovs_list);                            \
+         CONDITION_MULTIVAR_SAFE_LONG(VAR, PREV, MEMBER,                      \
+                                      ITER_VAR(VAR) != (LIST),                \
+                                      ITER_VAR(PREV) = ITER_VAR(VAR)->prev,   \
+                                      ITER_VAR(PREV) != (LIST));              \
+         UPDATE_MULTIVAR_SAFE_LONG(VAR, PREV))
+
+#define LIST_FOR_EACH_SAFE(VAR, NEXT, MEMBER, LIST)                           \
+    for (INIT_MULTIVAR_SAFE_LONG(VAR, NEXT, MEMBER, (LIST)->next,             \
+                                 struct ovs_list);                            \
+         CONDITION_MULTIVAR_SAFE_LONG(VAR, NEXT, MEMBER,                      \
+                                      ITER_VAR(VAR) != (LIST),                \
+                                      ITER_VAR(NEXT) = ITER_VAR(VAR)->next,   \
+                                      ITER_VAR(NEXT) != (LIST));              \
+         UPDATE_MULTIVAR_SAFE_LONG(VAR, NEXT))
+
+#define LIST_FOR_EACH_POP(ITER, MEMBER, LIST)                                 \
+    while (!ovs_list_is_empty(LIST) ?                                         \
+           (INIT_CONTAINER(ITER, ovs_list_pop_front(LIST), MEMBER), 1) :      \
+           (ITER = NULL, 0))
 
 /* Inline implementations. */