Simplify stack-allocated Lisp objects, and make them more portable.

The build_local_string macro was used in two ways: (1) string
literals for which scoped allocation suffices, and (2) file name
components, where it's not safe in general to assume bounded-size
ASCII data.  Simplify by defining a new macro SCOPED_STRING that
allocates a block-scope string, and by using SCOPED_STRING for (1)
and build_string for (2).  Furthermore, actually use stack
allocation only for objects known to have sufficient alignment.
This simpler implementation means Emacs can make
USE_STACK_LISP_OBJECTS the default unless GC_MARK_STACK !=
GC_MAKE_GCPROS_NOOPS.
* lisp.h (GCALIGNED): Align even if !USE_STACK_LISP_OBJECTS,
for fewer differences among implementations.
(struct Lisp_String): Now GCALIGNED.
(USE_STACK_LISP_OBJECTS): Default to true, since the
implementation no longer insists on a nonempty GCALIGNED.
But make it false if GC_MARK_STACK != GC_MAKE_GCPROS_NOOPS.
(SCOPED_CONS_INITIALIZER): Remove, since it's no longer needed
separately.  Move definiens to scoped_cons.  The old definition
was incorrect when GCALIGNED was defined to be empty.
(union Aligned_String): New type.
(USE_STACK_CONS, USE_STACK_STRING): New constants, so that the
implementation ports to compilers that don't align strictly enough.
Don't worry about the union sizes; it's not worth bothering about.
(scoped_cons, scoped_list1, scoped_list3, scoped_list4):
Rewrite using USE_STACK_CONS.
(scoped_cons): Assume the use of union Aligned_Cons.
(lisp_string_size, make_local_string, build_local_string): Remove.
Unless otherwise specified, all callers of build_local_string
changed to use SCOPED_STRING.
(SCOPED_STRING): New macro.
* data.c (wrong_choice):
* menu.c (single_menu_item):
* process.c (Fformat_network_address):
Hoist use of SCOPED_STRING out of a scope, so that its returned
object lives long enough.
* fileio.c (Fexpand_file_name): Use build_string, not SCOPED_STRING,
as the string might be long or might not be ASCII.

1 files changed, 8 insertions, 8 deletions

diff --git a/src/menu.c b/src/menu.c
index ea8da7a9d62..e63b21f0e08 100644
--- a/src/menu.c
+++ b/src/menu.c
@@ -354,7 +354,7 @@ single_menu_item (Lisp_Object key, Lisp_Object item, Lisp_Object dummy, void *sk
      front of them.  */
   if (!have_boxes ())
     {
-      Lisp_Object prefix = Qnil;
+      char const *prefix = 0;
       Lisp_Object type = AREF (item_properties, ITEM_PROPERTY_TYPE);
       if (!NILP (type))
         {
@@ -390,7 +390,7 @@ single_menu_item (Lisp_Object key, Lisp_Object item, Lisp_Object dummy, void *sk
                       if (!submenu && SREF (tem, 0) != '\0'
                           && SREF (tem, 0) != '-')
                         ASET (menu_items, idx + MENU_ITEMS_ITEM_NAME,
-                              concat2 (build_local_string ("    "), tem));
+                              concat2 (SCOPED_STRING ("    "), tem));
                       idx += MENU_ITEMS_ITEM_LENGTH;
                     }
                 }
@@ -399,24 +399,24 @@ single_menu_item (Lisp_Object key, Lisp_Object item, Lisp_Object dummy, void *sk
 
           /* Calculate prefix, if any, for this item.  */
           if (EQ (type, QCtoggle))
-            prefix = build_local_string (NILP (selected) ? "[ ] " : "[X] ");
+            prefix = NILP (selected) ? "[ ] " : "[X] ";
           else if (EQ (type, QCradio))
-            prefix = build_local_string (NILP (selected) ? "( ) " : "(*) ");
+            prefix = NILP (selected) ? "( ) " : "(*) ";
         }
       /* Not a button. If we have earlier buttons, then we need a prefix.  */
       else if (!skp->notbuttons && SREF (item_string, 0) != '\0'
                && SREF (item_string, 0) != '-')
-        prefix = build_local_string ("    ");
+        prefix = "    ";
 
-      if (!NILP (prefix))
-        item_string = concat2 (prefix, item_string);
+      if (prefix)
+        item_string = concat2 (SCOPED_STRING (prefix), item_string);
   }
 
   if ((FRAME_TERMCAP_P (XFRAME (Vmenu_updating_frame))
        || FRAME_MSDOS_P (XFRAME (Vmenu_updating_frame)))
       && !NILP (map))
     /* Indicate visually that this is a submenu.  */
-    item_string = concat2 (item_string, build_local_string (" >"));
+    item_string = concat2 (item_string, SCOPED_STRING (" >"));
 
   push_menu_item (item_string, enabled, key,
                   AREF (item_properties, ITEM_PROPERTY_DEF),