Move the attribute field of charsets to a separate vector

This simplifies the GC code, as this was the only field in the charset
struct that referenced the GC heap.  Without it, we no longer need to
trace the charset_table.

* src/charset.h (struct charset.attributes): Removed.
(charset_attributes_getter): New helper.
(CHARSET_ATTRIBUTES): Use it.
* src/charset.c (charset_attributes_table): New.
(Fdefine_charset_internal): Place attrs in charset_attributes_table.
(syms_of_charset): Initialize charset_attributes_table.
(mark_charset): Deleted.
* src/pdumper.c (dump_charset): Skip attributes field.
* src/lisp.h (mark_charset): Deleted.
* src/alloc.c (garbage_collect): mark_charset no longer needed.

src/alloc.c

@@ -5866,7 +5866,6 @@ garbage_collect (void)
   mark_terminals ();
   mark_kboards ();
   mark_threads ();
-  mark_charset ();
   mark_composite ();
   mark_profiler ();
 #ifdef HAVE_PGTK

src/charset.c

@@ -65,6 +65,12 @@ struct charset *charset_table;
 int charset_table_size;
 int charset_table_used;
 
+/* Table of attribute vectors.  charset_attributes_table[id] contains
+   the attribute vector for the charset at charset_table[id].
+
+   This is a separate vector to simplify GC.  */
+Lisp_Object charset_attributes_table;
+
 /* Special charsets corresponding to symbols.  */
 int charset_ascii;
 int charset_eight_bit;
@@ -1131,13 +1137,19 @@ usage: (define-charset-internal ...)  */)
 	     coding_system.charbuf[i] entries, which are 'int'.  */
 	  int old_size = charset_table_size;
 	  ptrdiff_t new_size = old_size;
-	  struct charset *new_table =
-	    xpalloc (0, &new_size, 1,
-		     min (INT_MAX, MOST_POSITIVE_FIXNUM),
-                     sizeof *charset_table);
-          memcpy (new_table, charset_table, old_size * sizeof *new_table);
-          charset_table = new_table;
+	  struct charset *new_table
+	    = xpalloc (0, &new_size, 1,
+		       min (INT_MAX, MOST_POSITIVE_FIXNUM),
+		       sizeof *charset_table);
+	  memcpy (new_table, charset_table,
+		  old_size * sizeof *new_table);
+	  charset_table = new_table;
 	  charset_table_size = new_size;
+	  Lisp_Object new_attr_table = make_vector (new_size, Qnil);
+	  for (size_t i = 0; i < old_size; i++)
+	    ASET (new_attr_table, i,
+		  AREF (charset_attributes_table, i));
+	  charset_attributes_table = new_attr_table;
 	  /* FIXME: This leaks memory, as the old charset_table becomes
 	     unreachable.  If the old charset table is charset_table_init
 	     then this leak is intentional; otherwise, it's unclear.
@@ -1152,8 +1164,9 @@ usage: (define-charset-internal ...)  */)
 
   ASET (attrs, charset_id, make_fixnum (id));
   charset.id = id;
-  charset.attributes = attrs;
   charset_table[id] = charset;
+  ASET (charset_attributes_table, id, attrs);
+  eassert (ASIZE (charset_attributes_table) == charset_table_size);
 
   if (charset.method == CHARSET_METHOD_MAP)
     {
@@ -2272,15 +2285,6 @@ See also `charset-priority-list' and `set-charset-priority'.  */)
   return charsets;
 }
 
-/* Not strictly necessary, because all charset attributes are also
-   reachable from `Vcharset_hash_table`.  */
-void
-mark_charset (void)
-{
-  for (int i = 0; i < charset_table_used; i++)
-    mark_object (charset_table[i].attributes);
-}
-
 
 void
 init_charset (void)
@@ -2383,6 +2387,9 @@ syms_of_charset (void)
   charset_table_used = 0;
   PDUMPER_REMEMBER_SCALAR (charset_table_used);
 
+  charset_attributes_table = make_vector (charset_table_size, Qnil);
+  staticpro (&charset_attributes_table);
+
   defsubr (&Scharsetp);
   defsubr (&Smap_charset_chars);
   defsubr (&Sdefine_charset_internal);

src/charset.h

@@ -150,8 +150,6 @@ struct charset
   /* Index to charset_table.  */
   int id;
 
-  Lisp_Object attributes;
-
   /* Dimension of the charset: 1, 2, 3, or 4.  */
   int dimension;
 
@@ -250,6 +248,8 @@ extern struct charset *charset_table;
 extern int charset_table_size;
 extern int charset_table_used;
 
+extern Lisp_Object charset_attributes_table;
+
 #define CHARSET_FROM_ID(id) (charset_table + (id))
 
 extern Lisp_Object Vcharset_ordered_list;
@@ -287,8 +287,14 @@ extern int emacs_mule_charset[256];
 #define CHARSET_SYMBOL_HASH_INDEX(symbol)	\
   hash_find (XHASH_TABLE (Vcharset_hash_table), symbol)
 
+INLINE Lisp_Object
+charset_attributes_getter (struct charset *charset)
+{
+  return AREF (charset_attributes_table, charset->id);
+}
+
 /* Return the attribute vector of CHARSET.  */
-#define CHARSET_ATTRIBUTES(charset) (charset)->attributes
+#define CHARSET_ATTRIBUTES(charset) (charset_attributes_getter (charset))
 
 #define CHARSET_ID(charset)		((charset)->id)
 #define CHARSET_DIMENSION(charset)	((charset)->dimension)

src/lisp.h

@@ -4226,7 +4226,6 @@ extern ptrdiff_t multibyte_chars_in_text (const unsigned char *, ptrdiff_t);
 extern void syms_of_character (void);
 
 /* Defined in charset.c.  */
-extern void mark_charset (void);
 extern void init_charset (void);
 extern void init_charset_once (void);
 extern void syms_of_charset (void);

src/pdumper.c

@@ -3208,7 +3208,7 @@ dump_object_for_offset (struct dump_context *ctx, Lisp_Object object)
 static dump_off
 dump_charset (struct dump_context *ctx, int cs_i)
 {
-#if CHECK_STRUCTS && !defined (HASH_charset_E31F4B5D96)
+#if CHECK_STRUCTS && !defined (HASH_charset_C9F4DCA7A7)
 # error "charset changed. See CHECK_STRUCTS comment in config.h."
 #endif
   /* We can't change the alignment here, because ctx->offset is what
@@ -3220,7 +3220,6 @@ dump_charset (struct dump_context *ctx, int cs_i)
   if (cs_i < charset_table_used) /* Don't look at uninitialized data.  */
     {
       DUMP_FIELD_COPY (&out, cs, id);
-      dump_field_lv (ctx, &out, cs, &cs->attributes, WEIGHT_NORMAL);
       DUMP_FIELD_COPY (&out, cs, dimension);
       memcpy (out.code_space, &cs->code_space, sizeof (cs->code_space));
       if (cs->code_space_mask)