diff --git a/gdk/gdkdmabufformats.c b/gdk/gdkdmabufformats.c
index 3e45e22ff9..5b7b19ef48 100644
--- a/gdk/gdkdmabufformats.c
+++ b/gdk/gdkdmabufformats.c
@@ -207,7 +207,8 @@ gdk_dmabuf_formats_new (GdkDmabufFormat *formats,
   self->n_formats = n_formats;
   self->formats = g_new (GdkDmabufFormat, n_formats);
 
-  memcpy (self->formats, formats, n_formats * sizeof (GdkDmabufFormat));
+  if (n_formats != 0)
+    memcpy (self->formats, formats, n_formats * sizeof (GdkDmabufFormat));
 
   return self;
 }
diff --git a/gtk/gtkcssnodedeclaration.c b/gtk/gtkcssnodedeclaration.c
index f170efc02b..3ea0d5219f 100644
--- a/gtk/gtkcssnodedeclaration.c
+++ b/gtk/gtkcssnodedeclaration.c
@@ -446,9 +446,9 @@ gtk_css_node_declaration_print (const GtkCssNodeDeclaration *decl,
 
   for (i = 0; i < sizeof (GtkStateFlags) * 8; i++)
     {
-      if (decl->state & (1 << i))
+      if (decl->state & (1u << i))
         {
-          const char *name = gtk_css_pseudoclass_name (1 << i);
+          const char *name = gtk_css_pseudoclass_name (1u << i);
           g_assert (name);
           g_string_append_c (string, ':');
           g_string_append (string, name);
diff --git a/gtk/gtksymbolicpaintable.c b/gtk/gtksymbolicpaintable.c
index 057be29742..0509eb5d9c 100644
--- a/gtk/gtksymbolicpaintable.c
+++ b/gtk/gtksymbolicpaintable.c
@@ -110,7 +110,8 @@ gtk_symbolic_paintable_snapshot_symbolic (GtkSymbolicPaintable   *paintable,
         [GTK_SYMBOLIC_COLOR_SUCCESS] = { 0.3046921492332342,0.6015716792553597, 0.023437857633325704, 1.0 }
       };
 
-      memcpy (real_colors, colors, sizeof (GdkRGBA) * n_colors);
+      if (n_colors != 0)
+        memcpy (real_colors, colors, sizeof (GdkRGBA) * n_colors);
 
       iface->snapshot_symbolic (paintable, snapshot, width, height, real_colors, 4);
     }
diff --git a/gtk/timsort/gtktimsort.c b/gtk/timsort/gtktimsort.c
index 67846674e2..daa7c113db 100644
--- a/gtk/timsort/gtktimsort.c
+++ b/gtk/timsort/gtktimsort.c
@@ -157,8 +157,9 @@ gtk_tim_sort_ensure_capacity (GtkTimSort *self,
       new_size |= new_size >> 4;
       new_size |= new_size >> 8;
       new_size |= new_size >> 16;
-      if (sizeof(new_size) > 4)
-        new_size |= new_size >> 32;
+#if GLIB_SIZEOF_SIZE_T > 4
+      new_size |= new_size >> 32;
+#endif
 
       new_size++;
       if (new_size == 0) /* (overflow) Not bloody likely! */