girepository: change giarginfo docs

Clarify the meaning of 'may be null' in the docs: it refers to the value
of the argument itself, not the reference to the argument.

https://bugzilla.gnome.org/show_bug.cgi?id=660879

1 files changed, 8 insertions, 3 deletions

diff --git a/girepository/giarginfo.c b/girepository/giarginfo.c
index c96976a8..083ca44d 100644
--- a/girepository/giarginfo.c
+++ b/girepository/giarginfo.c
@@ -125,7 +125,8 @@ g_arg_info_is_caller_allocates (GIArgInfo *info)
  * g_arg_info_is_optional:
  * @info: a #GIArgInfo
  *
- * Obtain if the argument is optional.
+ * Obtain if the argument is optional.  For 'out' arguments this means
+ * that you can pass %NULL in order to ignore the result.
  *
  * Returns: %TRUE if it is an optional argument
  */
@@ -147,9 +148,13 @@ g_arg_info_is_optional (GIArgInfo *info)
  * g_arg_info_may_be_null:
  * @info: a #GIArgInfo
  *
- * Obtain if the argument accepts %NULL.
+ * Obtain if the type of the argument includes the possibility of %NULL.
+ * For 'in' values this means that %NULL is a valid value.  For 'out'
+ * values, this means that %NULL may be returned.
  *
- * Returns: %TRUE if it accepts %NULL
+ * See also g_arg_info_is_optional().
+ *
+ * Returns: %TRUE if the value may be %NULL
  */
 gboolean
 g_arg_info_may_be_null (GIArgInfo *info)