libpkgconf: zero path lists after freeing

This is required to make the pointer safely re-usable after being freed,
otherwise the list still says that it has nodes, but they point nowhere.
This is particularly important for libpkgconf, if a caller needs to
re-enter the library after freeing a path in a static path (such as the
default personality)

libpkgconf/iter.h

@@ -34,6 +34,14 @@ typedef struct {
 
 #define PKGCONF_LIST_INITIALIZER		{ NULL, NULL, 0 }
 
+static inline void
+pkgconf_list_zero(pkgconf_list_t *list)
+{
+	list->head = NULL;
+	list->tail = NULL;
+	list->length = 0;
+}
+
 static inline void
 pkgconf_node_insert(pkgconf_node_t *node, void *data, pkgconf_list_t *list)
 {

libpkgconf/path.c

@@ -268,6 +268,8 @@ pkgconf_path_free(pkgconf_list_t *dirlist)
 		free(pnode->path);
 		free(pnode);
 	}
+
+	pkgconf_list_zero(dirlist);
 }
 
 static char *

libpkgconf/tuple.c

@@ -390,4 +390,6 @@ pkgconf_tuple_free(pkgconf_list_t *list)
 
 	PKGCONF_FOREACH_LIST_ENTRY_SAFE(list->head, next, node)
 		pkgconf_tuple_free_entry(node->data, list);
+
+	pkgconf_list_zero(list);
 }