[glib: 4/5] gprintf: Clarify error behaviour of g_vasprintf() in docs

[Sebastian Dröge <sdroege src gnome org>]

commit aa4385c1d97b36f1691fc58d2434bcc003a5a220
Author: Philip Withnall <pwithnall endlessos org>
Date:   Wed Mar 9 18:19:05 2022 +0000

    gprintf: Clarify error behaviour of g_vasprintf() in docs
    
    Signed-off-by: Philip Withnall <pwithnall endlessos org>

 glib/gprintf.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/glib/gprintf.c b/glib/gprintf.c
index 0e094f00f..7a8803351 100644
--- a/glib/gprintf.c
+++ b/glib/gprintf.c
@@ -295,7 +295,8 @@ g_vsnprintf (gchar   *string,
 
 /**
  * g_vasprintf:
- * @string: (not optional) (nullable): the return location for the newly-allocated string.
+ * @string: (not optional) (nullable): the return location for the newly-allocated string,
+ *   which will be %NULL if (and only if) this function fails
  * @format: (not nullable): a standard printf() format string, but notice
  *          [string precision pitfalls][string-precision]
  * @args: the list of arguments to insert in the output.
@@ -312,7 +313,7 @@ g_vsnprintf (gchar   *string,
  *
  * `glib/gprintf.h` must be explicitly included in order to use this function.
  *
- * Returns: the number of bytes printed.
+ * Returns: the number of bytes printed, or `-1` on failure
  *
  * Since: 2.4
  **/