Make it safe to delete keys while iterating with the json_object_object_foreach macro.

json_object.h

@@ -290,9 +290,10 @@ extern void json_object_object_del(struct json_object* obj, const char *key);
 /**
  * Iterate through all keys and values of an object.
  *
- * Adding or deleting keys to the object while iterating is NOT allowed.
+ * Adding keys to the object while iterating is NOT allowed.
  *
- * Replacing an existing key with a new value IS allowed.
+ * Deleting an existing key, or replacing an existing key with a
+ * new value IS allowed.
  *
  * @param obj the json_object instance
  * @param key the local name for the char* key variable defined in the body
@@ -304,12 +305,13 @@ extern void json_object_object_del(struct json_object* obj, const char *key);
 # define json_object_object_foreach(obj,key,val) \
 	char *key; \
 	struct json_object *val; \
-	for(struct lh_entry *entry = json_object_get_object(obj)->head; \
+	for(struct lh_entry *entry = json_object_get_object(obj)->head, *entry_next = NULL; \
 		({ if(entry) { \
 			key = (char*)entry->k; \
 			val = (struct json_object*)entry->v; \
+			entry_next = entry->next; \
 		} ; entry; }); \
-		entry = entry->next )
+		entry = entry_next )
 
 #else /* ANSI C or MSC */
 
@@ -317,12 +319,14 @@ extern void json_object_object_del(struct json_object* obj, const char *key);
 	char *key;\
 	struct json_object *val; \
 	struct lh_entry *entry; \
+	struct lh_entry *entry_next = NULL; \
 	for(entry = json_object_get_object(obj)->head; \
 		(entry ? ( \
 			key = (char*)entry->k, \
 			val = (struct json_object*)entry->v, \
+			entry_next = entry->next, \
 			entry) : 0); \
-		entry = entry->next)
+		entry = entry_next)
 
 #endif /* defined(__GNUC__) && !defined(__STRICT_ANSI__) */
 

tests/testReplaceExisting.c

@@ -16,9 +16,29 @@ int main(int argc, char **argv)
 	json_object *my_object = json_object_new_object();
 	json_object_object_add(my_object, "foo1", json_object_new_string("bar1"));
 	json_object_object_add(my_object, "foo2", json_object_new_string("bar2"));
+	json_object_object_add(my_object, "deleteme", json_object_new_string("bar2"));
 	json_object_object_add(my_object, "foo3", json_object_new_string("bar3"));
-	const char *original_key = NULL;
+
+	printf("==== delete-in-loop test starting ====\n");
+
 	int orig_count = 0;
+	json_object_object_foreach(my_object, key0, val0)
+	{
+		printf("Key at index %d is [%s]", orig_count, key0);
+		if (strcmp(key0, "deleteme") == 0)
+		{
+			json_object_object_del(my_object, key0);
+			printf(" (deleted)\n");
+		}
+		else
+			printf(" (kept)\n");
+		orig_count++;
+	}
+
+	printf("==== replace-value first loop starting ====\n");
+
+	const char *original_key = NULL;
+	orig_count = 0;
 	json_object_object_foreach(my_object, key, val)
 	{
 		printf("Key at index %d is [%s]\n", orig_count, key);

tests/testReplaceExisting.expected

@@ -1,3 +1,9 @@
+==== delete-in-loop test starting ====
+Key at index 0 is [foo1] (kept)
+Key at index 1 is [foo2] (kept)
+Key at index 2 is [deleteme] (deleted)
+Key at index 3 is [foo3] (kept)
+==== replace-value first loop starting ====
 Key at index 0 is [foo1]
 Key at index 1 is [foo2]
 replacing value for key [foo2]