Pacify GCC 10.1.0

Pacify GCC 10.1.0 so that it does not issue false alarms
when Emacs is configured with --enable-gcc-warnings.
* src/dispnew.c (clear_glyph_row):
* src/fns.c (hash_clear):
* src/keyboard.c (append_tab_bar_item):
* src/lisp.h (vcopy):
* src/xfaces.c (get_lface_attributes_no_remap)
(Finternal_copy_lisp_face, realize_default_face):
* src/xmenu.c (set_frame_menubar):
Work around -Warray-bounds false alarm in GCC 10.1.0.
* src/intervals.c (copy_properties):
Avoid -Wnull-dereference false alarm in GCC 10.1.0.
* src/lisp.h (xvector_contents_addr, xvector_contents):
New functions, useful for working around GCC bug 95072.

src/dispnew.c

@@ -881,7 +881,7 @@ clear_glyph_row (struct glyph_row *row)
   enum { off = offsetof (struct glyph_row, used) };
 
   /* Zero everything except pointers in `glyphs'.  */
-  memset (row->used, 0, sizeof *row - off);
+  memset ((char *) row + off, 0, sizeof *row - off);
 }
 
 

src/fns.c

@@ -4392,7 +4392,7 @@ hash_clear (struct Lisp_Hash_Table *h)
     {
       ptrdiff_t size = HASH_TABLE_SIZE (h);
       if (!hash_rehash_needed_p (h))
-	memclear (XVECTOR (h->hash)->contents, size * word_size);
+	memclear (xvector_contents (h->hash), size * word_size);
       for (ptrdiff_t i = 0; i < size; i++)
 	{
 	  set_hash_next_slot (h, i, i < size - 1 ? i + 1 : -1);

src/intervals.c

@@ -117,10 +117,11 @@ create_root_interval (Lisp_Object parent)
 /* Make the interval TARGET have exactly the properties of SOURCE.  */
 
 void
-copy_properties (register INTERVAL source, register INTERVAL target)
+copy_properties (INTERVAL source, INTERVAL target)
 {
   if (DEFAULT_INTERVAL_P (source) && DEFAULT_INTERVAL_P (target))
     return;
+  eassume (source && target);
 
   COPY_INTERVAL_CACHE (source, target);
   set_interval_plist (target, Fcopy_sequence (source->plist));

src/keyboard.c

@@ -8302,7 +8302,7 @@ append_tab_bar_item (void)
   /* Append entries from tab_bar_item_properties to the end of
      tab_bar_items_vector.  */
   vcopy (tab_bar_items_vector, ntab_bar_items,
-	 XVECTOR (tab_bar_item_properties)->contents, TAB_BAR_ITEM_NSLOTS);
+	 xvector_contents (tab_bar_item_properties), TAB_BAR_ITEM_NSLOTS);
   ntab_bar_items += TAB_BAR_ITEM_NSLOTS;
 }
 
@@ -8779,7 +8779,7 @@ append_tool_bar_item (void)
   /* Append entries from tool_bar_item_properties to the end of
      tool_bar_items_vector.  */
   vcopy (tool_bar_items_vector, ntool_bar_items,
-	 XVECTOR (tool_bar_item_properties)->contents, TOOL_BAR_ITEM_NSLOTS);
+	 xvector_contents (tool_bar_item_properties), TOOL_BAR_ITEM_NSLOTS);
   ntool_bar_items += TOOL_BAR_ITEM_NSLOTS;
 }
 

src/lisp.h

@@ -3350,6 +3350,27 @@ struct frame;
 #define HAVE_EXT_TOOL_BAR true
 #endif
 
+/* Return the address of vector A's element at index I.  */
+
+INLINE Lisp_Object *
+xvector_contents_addr (Lisp_Object a, ptrdiff_t i)
+{
+  /* This should return &XVECTOR (a)->contents[i], but that would run
+     afoul of GCC bug 95072.  */
+  void *v = XVECTOR (a);
+  char *p = v;
+  void *w = p + header_size + i * word_size;
+  return w;
+}
+
+/* Return the address of vector A's elements.  */
+
+INLINE Lisp_Object *
+xvector_contents (Lisp_Object a)
+{
+  return xvector_contents_addr (a, 0);
+}
+
 /* Copy COUNT Lisp_Objects from ARGS to contents of V starting from OFFSET.  */
 
 INLINE void
@@ -3357,7 +3378,7 @@ vcopy (Lisp_Object v, ptrdiff_t offset, Lisp_Object const *args,
        ptrdiff_t count)
 {
   eassert (0 <= offset && 0 <= count && offset + count <= ASIZE (v));
-  memcpy (XVECTOR (v)->contents + offset, args, count * sizeof *args);
+  memcpy (xvector_contents_addr (v, offset), args, count * sizeof *args);
 }
 
 /* Functions to modify hash tables.  */

src/xfaces.c

@@ -1888,7 +1888,7 @@ get_lface_attributes_no_remap (struct frame *f, Lisp_Object face_name,
   lface = lface_from_face_name_no_resolve (f, face_name, signal_p);
 
   if (! NILP (lface))
-    memcpy (attrs, XVECTOR (lface)->contents,
+    memcpy (attrs, xvector_contents (lface),
 	    LFACE_VECTOR_SIZE * sizeof *attrs);
 
   return !NILP (lface);
@@ -2860,7 +2860,7 @@ The value is TO.  */)
       f = XFRAME (new_frame);
     }
 
-  vcopy (copy, 0, XVECTOR (lface)->contents, LFACE_VECTOR_SIZE);
+  vcopy (copy, 0, xvector_contents (lface), LFACE_VECTOR_SIZE);
 
   /* Changing a named face means that all realized faces depending on
      that face are invalid.  Since we cannot tell which realized faces
@@ -5598,7 +5598,7 @@ realize_default_face (struct frame *f)
   /* Realize the face; it must be fully-specified now.  */
   eassert (lface_fully_specified_p (XVECTOR (lface)->contents));
   check_lface (lface);
-  memcpy (attrs, XVECTOR (lface)->contents, sizeof attrs);
+  memcpy (attrs, xvector_contents (lface), sizeof attrs);
   struct face *face = realize_face (c, attrs, DEFAULT_FACE_ID);
 
 #ifndef HAVE_WINDOW_SYSTEM

src/xmenu.c

@@ -763,7 +763,7 @@ set_frame_menubar (struct frame *f, bool first_time, bool deep_p)
 
       /* Save the frame's previous menu bar contents data.  */
       if (previous_menu_items_used)
-	memcpy (previous_items, XVECTOR (f->menu_bar_vector)->contents,
+	memcpy (previous_items, xvector_contents (f->menu_bar_vector),
 		previous_menu_items_used * word_size);
 
       /* Fill in menu_items with the current menu bar contents.