util: Rework virStringListAdd

So every caller does the same: they use virStringListAdd() to add
new item into the list and then free the old copy to replace it
with new list. It's not very memory effective, nor environmental
friendly.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

src/util/virmacmap.c

@@ -90,7 +90,6 @@ virMacMapAddLocked(virMacMapPtr mgr,
 {
     int ret = -1;
     char **macsList = NULL;
-    char **newMacsList = NULL;
 
     if ((macsList = virHashLookup(mgr->macs, domain)) &&
         virStringListHasString((const char**) macsList, mac)) {
@@ -98,15 +97,12 @@ virMacMapAddLocked(virMacMapPtr mgr,
         goto cleanup;
     }
 
-    if (!(newMacsList = virStringListAdd((const char **) macsList, mac)) ||
-        virHashUpdateEntry(mgr->macs, domain, newMacsList) < 0)
+    if (virStringListAdd(&macsList, mac) < 0 ||
+        virHashUpdateEntry(mgr->macs, domain, macsList) < 0)
         goto cleanup;
-    newMacsList = NULL;
-    virStringListFree(macsList);
 
     ret = 0;
  cleanup:
-    virStringListFree(newMacsList);
     return ret;
 }
 

src/util/virstring.c

@@ -175,32 +175,23 @@ char *virStringListJoin(const char **strings,
  * @strings: a NULL-terminated array of strings
  * @item: string to add
  *
- * Creates new strings list with all strings duplicated and @item
- * at the end of the list. Callers is responsible for freeing
- * both @strings and returned list.
+ * Appends @item into string list @strings. If *@strings is not
+ * allocated yet new string list is created.
+ *
+ * Returns: 0 on success,
+ *         -1 otherwise
  */
-char **
-virStringListAdd(const char **strings,
+int
+virStringListAdd(char ***strings,
                  const char *item)
 {
-    char **ret = NULL;
-    size_t i = virStringListLength(strings);
-
-    if (VIR_ALLOC_N(ret, i + 2) < 0)
-        goto error;
-
-    for (i = 0; strings && strings[i]; i++) {
-        if (VIR_STRDUP(ret[i], strings[i]) < 0)
-            goto error;
-    }
+    size_t i = virStringListLength((const char **) *strings);
 
-    if (VIR_STRDUP(ret[i], item) < 0)
-        goto error;
+    if (VIR_EXPAND_N(*strings, i, 2) < 0 ||
+        VIR_STRDUP((*strings)[i - 2], item) < 0)
+        return -1;
 
-    return ret;
- error:
-    virStringListFree(ret);
-    return NULL;
+    return 0;
 }
 
 

src/util/virstring.h

@@ -44,7 +44,7 @@ char *virStringListJoin(const char **strings,
                         const char *delim)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
 
-char **virStringListAdd(const char **strings,
+int virStringListAdd(char ***strings,
                      const char *item);
 void virStringListRemove(char ***strings,
                          const char *item);

tests/virstringtest.c

@@ -179,12 +179,8 @@ static int testAdd(const void *args)
     size_t i;
 
     for (i = 0; data->tokens[i]; i++) {
-        char **tmp = virStringListAdd((const char **)list, data->tokens[i]);
-        if (!tmp)
+        if (virStringListAdd(&list, data->tokens[i]) < 0)
             goto cleanup;
-        virStringListFree(list);
-        list = tmp;
-        tmp = NULL;
     }
 
     if (!list &&