diff --git a/glib/garray.c b/glib/garray.c
index a4762842f..5670408fd 100644
--- a/glib/garray.c
+++ b/glib/garray.c
@@ -1503,7 +1503,8 @@ g_ptr_array_sort_with_data (GPtrArray        *array,
  * @func: the function to call for each array element
  * @user_data: user data to pass to the function
  * 
- * Calls a function for each element of a #GPtrArray.
+ * Calls a function for each element of a #GPtrArray. @func must not
+ * add elements to or remove elements from the array.
  *
  * Since: 2.4
  */
diff --git a/glib/gdataset.c b/glib/gdataset.c
index ae36e9e2f..cc4397ca5 100644
--- a/glib/gdataset.c
+++ b/glib/gdataset.c
@@ -1065,8 +1065,12 @@ g_datalist_get_data (GData	 **datalist,
  *
  * Calls the given function for each data element which is associated
  * with the given location. Note that this function is NOT thread-safe.
- * So unless @datalist can be protected from any modifications during
- * invocation of this function, it should not be called.
+ * So unless @dataset_location can be protected from any modifications
+ * during invocation of this function, it should not be called.
+ *
+ * @func can make changes to the dataset, but the iteration will not
+ * reflect changes made during the g_dataset_foreach() call, other
+ * than skipping over elements that are removed.
  **/
 void
 g_dataset_foreach (gconstpointer    dataset_location,
@@ -1104,6 +1108,10 @@ g_dataset_foreach (gconstpointer    dataset_location,
  * function is NOT thread-safe. So unless @datalist can be protected
  * from any modifications during invocation of this function, it should
  * not be called.
+ *
+ * @func can make changes to @datalist, but the iteration will not
+ * reflect changes made during the g_datalist_foreach() call, other
+ * than skipping over elements that are removed.
  **/
 void
 g_datalist_foreach (GData	   **datalist,
diff --git a/glib/glist.c b/glib/glist.c
index 2b5692ee9..6f2079a4c 100644
--- a/glib/glist.c
+++ b/glib/glist.c
@@ -211,6 +211,9 @@ g_list_free_1 (GList *list)
  * Convenience method, which frees all the memory used by a #GList,
  * and calls @free_func on every element's data.
  *
+ * @free_func must not modify the list (eg, by removing the freed
+ * element from it).
+ *
  * Since: 2.28
  */
 void
@@ -985,6 +988,9 @@ g_list_length (GList *list)
  * @user_data: user data to pass to the function
  *
  * Calls a function for each element of a #GList.
+ *
+ * It is safe for @func to remove the element from @list, but it must
+ * not modify any part of the list after that element.
  */
 /**
  * GFunc:
diff --git a/glib/gnode.c b/glib/gnode.c
index 51c9fdc80..9d5ff5792 100644
--- a/glib/gnode.c
+++ b/glib/gnode.c
@@ -816,6 +816,7 @@ g_node_depth_traverse_level (GNode             *node,
  * Traverses a tree starting at the given root #GNode.
  * It calls the given function for each node visited.
  * The traversal can be halted at any point by returning %TRUE from @func.
+ * @func must not do anything that would modify the structure of the tree.
  */
 
 /**
@@ -1235,8 +1236,9 @@ g_node_last_sibling (GNode *node)
  * @func: the function to call for each visited node
  * @data: user data to pass to the function
  *
- * Calls a function for each of the children of a #GNode.
- * Note that it doesn't descend beneath the child nodes.
+ * Calls a function for each of the children of a #GNode. Note that it
+ * doesn't descend beneath the child nodes. @func must not do anything
+ * that would modify the structure of the tree.
  */
 /**
  * GNodeForeachFunc:
diff --git a/glib/gqueue.c b/glib/gqueue.c
index 01bd13439..26fe507a3 100644
--- a/glib/gqueue.c
+++ b/glib/gqueue.c
@@ -95,6 +95,9 @@ g_queue_free (GQueue *queue)
  * Convenience method, which frees all the memory used by a #GQueue,
  * and calls the specified destroy function on every element's data.
  *
+ * @free_func should not modify the queue (eg, by removing the freed
+ * element from it).
+ *
  * Since: 2.32
  */
 void
@@ -231,6 +234,9 @@ g_queue_copy (GQueue *queue)
  * Calls @func for each element in the queue passing @user_data to the
  * function.
  * 
+ * It is safe for @func to remove the element from @queue, but it must
+ * not modify any part of the queue after that element.
+ *
  * Since: 2.4
  */
 void
diff --git a/glib/gsequence.c b/glib/gsequence.c
index a67f2576f..2dac88a94 100644
--- a/glib/gsequence.c
+++ b/glib/gsequence.c
@@ -294,7 +294,8 @@ g_sequence_free (GSequence *seq)
  * @user_data: user data passed to @func
  *
  * Calls @func for each item in the range (@begin, @end) passing
- * @user_data to the function.
+ * @user_data to the function. @func must not modify the sequence
+ * itself.
  *
  * Since: 2.14
  */
@@ -335,7 +336,7 @@ g_sequence_foreach_range (GSequenceIter *begin,
  * @user_data: user data passed to @func
  *
  * Calls @func for each item in the sequence passing @user_data
- * to the function.
+ * to the function. @func must not modify the sequence itself.
  *
  * Since: 2.14
  */
diff --git a/glib/gslist.c b/glib/gslist.c
index 028237d3d..bc29b4101 100644
--- a/glib/gslist.c
+++ b/glib/gslist.c
@@ -165,6 +165,9 @@ g_slist_free_1 (GSList *list)
  * Convenience method, which frees all the memory used by a #GSList, and
  * calls the specified destroy function on every element's data.
  *
+ * @free_func must not modify the list (eg, by removing the freed
+ * element from it).
+ *
  * Since: 2.28
  **/
 void
@@ -844,6 +847,9 @@ g_slist_length (GSList *list)
  * @user_data: user data to pass to the function
  *
  * Calls a function for each element of a #GSList.
+ *
+ * It is safe for @func to remove the element from @list, but it must
+ * not modify any part of the list after that element.
  */
 void
 g_slist_foreach (GSList   *list,