Also fix query_plans_by_table

[collectd.git] / src / meta_data.c

diff --git a/src/meta_data.c b/src/meta_data.c
index b502b37..d220784 100644 (file)
--- a/src/meta_data.c
+++ b/src/meta_data.c
@@ -109,6 +109,8 @@ static meta_entry_t *md_entry_clone (const meta_entry_t *orig) /* {{{ */
     return (NULL);
 
   copy = md_entry_alloc (orig->key);
+  if (copy == NULL)
+    return (NULL);
   copy->type = orig->type;
   if (copy->type == MD_TYPE_STRING)
     copy->value.mv_string = strdup (orig->value.mv_string);
@@ -207,6 +209,17 @@ static meta_entry_t *md_entry_lookup (meta_data_t *md, /* {{{ */
 } /* }}} meta_entry_t *md_entry_lookup */
 
 /*
+ * Each value_list_t*, as it is going through the system, is handled by exactly
+ * one thread. Plugins which pass a value_list_t* to another thread, e.g. the
+ * rrdtool plugin, must create a copy first. The meta data within a
+ * value_list_t* is not thread safe and doesn't need to be.
+ *
+ * The meta data associated with cache entries are a different story. There, we
+ * need to ensure exclusive locking to prevent leaks and other funky business.
+ * This is ensured by the uc_meta_data_get_*() functions.
+ */
+
+/*
  * Public functions
  */
 meta_data_t *meta_data_create (void) /* {{{ */
@@ -312,7 +325,13 @@ int meta_data_toc (meta_data_t *md, char ***toc) /* {{{ */
   for (e = md->head; e != NULL; e = e->next)
     ++count;    
 
-  *toc = malloc(count * sizeof(**toc));
+  if (count == 0)
+  {
+    pthread_mutex_unlock (&md->lock);
+    return (count);
+  }
+
+  *toc = calloc(count, sizeof(**toc));
   for (e = md->head; e != NULL; e = e->next)
     (*toc)[i++] = strdup(e->key);
   
@@ -482,7 +501,7 @@ int meta_data_get_string (meta_data_t *md, /* {{{ */
 
   if (e->type != MD_TYPE_STRING)
   {
-    ERROR ("meta_data_get_signed_int: Type mismatch for key `%s'", e->key);
+    ERROR ("meta_data_get_string: Type mismatch for key `%s'", e->key);
     pthread_mutex_unlock (&md->lock);
     return (-ENOENT);
   }