diff --git a/gtk/gtkcheckbutton.c b/gtk/gtkcheckbutton.c
index 366fd2398c..e9a30a1ce3 100644
--- a/gtk/gtkcheckbutton.c
+++ b/gtk/gtkcheckbutton.c
@@ -913,6 +913,8 @@ gtk_check_button_set_label (GtkCheckButton *self,
  * Setting the group of a check button also changes the css name of the
  * indicator widget's CSS node to 'radio'.
  *
+ * Setting up groups in a cycle leads to undefined behavior.
+ *
  * Note that the same effect can be achieved via the [interface@Gtk.Actionable]
  * API, by using the same action with parameter type and state type 's'
  * for all buttons in the group, and giving each button its own target
@@ -926,6 +928,7 @@ gtk_check_button_set_group (GtkCheckButton *self,
   GtkCheckButtonPrivate *group_priv = gtk_check_button_get_instance_private (group);
 
   g_return_if_fail (GTK_IS_CHECK_BUTTON (self));
+  g_return_if_fail (self != group);
 
   if (!group)
     {
diff --git a/gtk/gtkcssshadowvalue.c b/gtk/gtkcssshadowvalue.c
index 86dfcafdfb..94fccffd82 100644
--- a/gtk/gtkcssshadowvalue.c
+++ b/gtk/gtkcssshadowvalue.c
@@ -494,14 +494,14 @@ gtk_css_shadow_value_parse (GtkCssParser *parser,
     return gtk_css_shadow_value_new_none ();
 
   do {
+    if (n_shadows == MAX_SHADOWS)
+      {
+        gtk_css_parser_error_syntax (parser, "Not more than %d shadows supported", MAX_SHADOWS);
+        goto fail;
+      }
     if (gtk_css_shadow_value_parse_one (parser, box_shadow_mode, &shadows[n_shadows]))
       n_shadows++;
 
-    if (n_shadows > MAX_SHADOWS)
-      {
-        gtk_css_parser_error_syntax (parser, "Not more than 64 shadows supported");
-        goto fail;
-      }
   } while (gtk_css_parser_try_token (parser, GTK_CSS_TOKEN_COMMA));
 
   return gtk_css_shadow_value_new (shadows, n_shadows, FALSE);
diff --git a/gtk/gtksizerequest.c b/gtk/gtksizerequest.c
index a8d4ff7763..bad631c022 100644
--- a/gtk/gtksizerequest.c
+++ b/gtk/gtksizerequest.c
@@ -698,6 +698,7 @@ gtk_distribute_natural_allocation (int               extra_space,
   int    i;
 
   g_return_val_if_fail (extra_space >= 0, 0);
+  g_return_val_if_fail (n_requested_sizes > 0, 0);
 
   spreading = g_newa (guint, n_requested_sizes);
 
diff --git a/gtk/gtktogglebutton.c b/gtk/gtktogglebutton.c
index 6ae96fc8af..1e53a896c6 100644
--- a/gtk/gtktogglebutton.c
+++ b/gtk/gtktogglebutton.c
@@ -473,6 +473,8 @@ gtk_toggle_button_toggled (GtkToggleButton *toggle_button)
  * In a group of multiple toggle buttons, only one button can be active
  * at a time.
  *
+ * Setting up groups in a cycle leads to undefined behavior.
+ *
  * Note that the same effect can be achieved via the [interface@Gtk.Actionable]
  * API, by using the same action with parameter type and state type 's'
  * for all buttons in the group, and giving each button its own target
@@ -486,6 +488,7 @@ gtk_toggle_button_set_group (GtkToggleButton *toggle_button,
   GtkToggleButtonPrivate *group_priv = gtk_toggle_button_get_instance_private (group);
 
   g_return_if_fail (GTK_IS_TOGGLE_BUTTON (toggle_button));
+  g_return_if_fail (toggle_button != group);
 
   if (!group)
     {
diff --git a/gtk/gtktreestore.c b/gtk/gtktreestore.c
index c02dcd3a17..c542af00ba 100644
--- a/gtk/gtktreestore.c
+++ b/gtk/gtktreestore.c
@@ -2471,7 +2471,9 @@ gtk_tree_store_move (GtkTreeStore *tree_store,
   GNode *parent, *node, *a, *b, *tmp, *tmp_a, *tmp_b;
   int old_pos, new_pos, length, i, *order;
   GtkTreePath *path = NULL, *tmppath, *pos_path = NULL;
-  GtkTreeIter parent_iter, dst_a, dst_b;
+  GtkTreeIter parent_iter = { 0, };
+  GtkTreeIter dst_a = { 0, };
+  GtkTreeIter dst_b = { 0, };
   int depth = 0;
   gboolean handle_b = TRUE;
 
diff --git a/modules/printbackends/gtkprintbackendlpr.c b/modules/printbackends/gtkprintbackendlpr.c
index 17ed4fbf3f..ea7770f5a9 100644
--- a/modules/printbackends/gtkprintbackendlpr.c
+++ b/modules/printbackends/gtkprintbackendlpr.c
@@ -103,7 +103,7 @@ char **
 g_io_module_query (void)
 {
   char *eps[] = {
-    GTK_PRINT_BACKEND_EXTENSION_POINT_NAME,
+    (char *)GTK_PRINT_BACKEND_EXTENSION_POINT_NAME,
     NULL
   };
 
@@ -399,13 +399,12 @@ lpr_printer_get_options (GtkPrinter           *printer,
   GtkPrinterOptionSet *set;
   GtkPrinterOption *option;
   const char *command;
-  char *n_up[] = {"1", "2", "4", "6", "9", "16" };
+  const char *n_up[] = {"1", "2", "4", "6", "9", "16" };
 
   set = gtk_printer_option_set_new ();
 
   option = gtk_printer_option_new ("gtk-n-up", _("Pages Per Sheet"), GTK_PRINTER_OPTION_TYPE_PICKONE);
-  gtk_printer_option_choices_from_array (option, G_N_ELEMENTS (n_up),
-                                         (char **)n_up, (char **)n_up);
+  gtk_printer_option_choices_from_array (option, G_N_ELEMENTS (n_up), n_up, n_up);
   gtk_printer_option_set (option, "1");
   gtk_printer_option_set_add (set, option);
   g_object_unref (option);
diff --git a/subprojects/gtk-doc.wrap b/subprojects/gtk-doc.wrap
deleted file mode 100644
index 79ec37220a..0000000000
--- a/subprojects/gtk-doc.wrap
+++ /dev/null
@@ -1,5 +0,0 @@
-[wrap-git]
-directory=gtk-doc
-url=https://gitlab.gnome.org/GNOME/gtk-doc.git
-revision=master
-depth=1