Make variable forwarding explicit rather the using special values.

Basically, this makes the structure of buffer-local values and object
forwarding explicit in the type of Lisp_Symbols rather than use
special Lisp_Objects for that.  This tends to lead to slightly more
verbose code, but is more C-like, simpler, and makes it easier to make
sure we handled all cases, among other things by letting the compiler
help us check it.
* lisp.h (enum Lisp_Misc_Type, union Lisp_Misc):
Removing forwarding objects.
(enum Lisp_Fwd_Type, enum symbol_redirect, union Lisp_Fwd): New types.
(struct Lisp_Symbol): Make the various forms of variable-forwarding
explicit rather than hiding them inside Lisp_Object "values".
(XFWDTYPE): New macro.
(XINTFWD, XBOOLFWD, XOBJFWD, XKBOARD_OBJFWD): Redefine.
(XBUFFER_LOCAL_VALUE): Remove.
(SYMBOL_VAL, SYMBOL_ALIAS, SYMBOL_BLV, SYMBOL_FWD, SET_SYMBOL_VAL)
(SET_SYMBOL_ALIAS, SET_SYMBOL_BLV, SET_SYMBOL_FWD): New macros.
(SYMBOL_VALUE, SET_SYMBOL_VALUE): Remove.
(struct Lisp_Intfwd, struct Lisp_Boolfwd, struct Lisp_Objfwd)
(struct Lisp_Buffer_Objfwd, struct Lisp_Kboard_Objfwd):
Remove the Lisp_Misc_* header.
(struct Lisp_Buffer_Local_Value): Redefine.
(BLV_FOUND, SET_BLV_FOUND, BLV_VALUE, SET_BLV_VALUE): New macros.
(struct Lisp_Misc_Any): Add filler to get the right size.
(struct Lisp_Free): Use struct Lisp_Misc_Any rather than struct
Lisp_Intfwd.
(DEFVAR_LISP, DEFVAR_LISP_NOPRO, DEFVAR_BOOL, DEFVAR_INT)
(DEFVAR_KBOARD): Allocate a forwarding object.
* data.c (do_blv_forwarding, store_blv_forwarding): New macros.
(let_shadows_global_binding_p): New function.
(union Lisp_Val_Fwd): New type.
(make_blv): New function.
(swap_in_symval_forwarding, indirect_variable, do_symval_forwarding)
(store_symval_forwarding, swap_in_global_binding, Fboundp)
(swap_in_symval_forwarding, find_symbol_value, Fset)
(let_shadows_buffer_binding_p, set_internal, default_value)
(Fset_default, Fmake_variable_buffer_local, Fmake_local_variable)
(Fkill_local_variable, Fmake_variable_frame_local)
(Flocal_variable_p, Flocal_variable_if_set_p)
(Fvariable_binding_locus):
* xdisp.c (select_frame_for_redisplay):
* lread.c (Fintern, Funintern, init_obarray, defvar_int)
(defvar_bool, defvar_lisp_nopro, defvar_lisp, defvar_kboard):
* frame.c (store_frame_param):
* eval.c (Fdefvaralias, Fuser_variable_p, specbind, unbind_to):
* bytecode.c (Fbyte_code) <varref, varset>: Adapt to the new symbol
value structure.
* buffer.c (PER_BUFFER_SYMBOL): Move from buffer.h.
(clone_per_buffer_values): Only adjust markers into the current buffer.
(reset_buffer_local_variables): PER_BUFFER_IDX is never -2.
(Fbuffer_local_value, set_buffer_internal_1)
(swap_out_buffer_local_variables):
Adapt to the new symbol value structure.
(DEFVAR_PER_BUFFER): Allocate a Lisp_Buffer_Objfwd object.
(defvar_per_buffer): Take a new arg for the fwd object.
(buffer_lisp_local_variables): Return a proper alist (different fix
for bug#4138).
* alloc.c (Fmake_symbol): Use SET_SYMBOL_VAL.
(Fgarbage_collect): Don't handle buffer_defaults specially.
(mark_object): Handle new symbol value structure rather than the old
special Lisp_Misc_* objects.
(gc_sweep) <symbols>: Free also the buffer-local-value objects.
* term.c (set_tty_color_mode):
* bidi.c (bidi_initialize): Don't access the ->value field directly.
* buffer.h (PER_BUFFER_VAR_OFFSET): Don't bother with
a buffer_local_flags.
* print.c (print_object): Get rid of impossible forwarding objects.

1 files changed, 35 insertions, 35 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 37ec06c7be1..c1f1094d15f 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -1365,7 +1365,7 @@ uninterrupt_malloc ()
   pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_RECURSIVE);
   pthread_mutex_init (&alloc_mutex, &attr);
 #else  /* !DOUG_LEA_MALLOC */
-  /* Some systems such as Solaris 2.6 doesn't have a recursive mutex,
+  /* Some systems such as Solaris 2.6 don't have a recursive mutex,
      and the bundled gmalloc.c doesn't require it.  */
   pthread_mutex_init (&alloc_mutex, NULL);
 #endif /* !DOUG_LEA_MALLOC */
@@ -3193,13 +3193,13 @@ Its value and function definition are void, and its property list is nil.  */)
   p = XSYMBOL (val);
   p->xname = name;
   p->plist = Qnil;
-  p->value = Qunbound;
+  p->redirect = SYMBOL_PLAINVAL;
+  SET_SYMBOL_VAL (p, Qunbound);
   p->function = Qunbound;
   p->next = NULL;
   p->gcmarkbit = 0;
   p->interned = SYMBOL_UNINTERNED;
   p->constant = 0;
-  p->indirect_variable = 0;
   consing_since_gc += sizeof (struct Lisp_Symbol);
   symbols_consed++;
   return val;
@@ -5581,17 +5581,42 @@ mark_object (arg)
           break;
         CHECK_ALLOCATED_AND_LIVE (live_symbol_p);
         ptr->gcmarkbit = 1;
-        mark_object (ptr->value);
         mark_object (ptr->function);
         mark_object (ptr->plist);
-
+        switch (ptr->redirect)
+          {
+          case SYMBOL_PLAINVAL: mark_object (SYMBOL_VAL (ptr)); break;
+          case SYMBOL_VARALIAS:
+            {
+              Lisp_Object tem;
+              XSETSYMBOL (tem, SYMBOL_ALIAS (ptr));
+              mark_object (tem);
+              break;
+            }
+          case SYMBOL_LOCALIZED:
+            {
+              struct Lisp_Buffer_Local_Value *blv = SYMBOL_BLV (ptr);
+              /* If the value is forwarded to a buffer or keyboard field,
+                 these are marked when we see the corresponding object.
+                 And if it's forwarded to a C variable, either it's not
+                 a Lisp_Object var, or it's staticpro'd already.  */
+              mark_object (blv->where);
+              mark_object (blv->valcell);
+              mark_object (blv->defcell);
+              break;
+            }
+          case SYMBOL_FORWARDED:
+            /* If the value is forwarded to a buffer or keyboard field,
+               these are marked when we see the corresponding object.
+               And if it's forwarded to a C variable, either it's not
+               a Lisp_Object var, or it's staticpro'd already.  */
+            break;
+          default: abort ();
+          }
         if (!PURE_POINTER_P (XSTRING (ptr->xname)))
           MARK_STRING (XSTRING (ptr->xname));
         MARK_INTERVAL_TREE (STRING_INTERVALS (ptr->xname));
 
-        /* Note that we do not mark the obarray of the symbol.
-           It is safe not to do so because nothing accesses that
-           slot except to check whether it is nil.  */
         ptr = ptr->next;
         if (ptr)
           {
@@ -5610,22 +5635,6 @@ mark_object (arg)
 
       switch (XMISCTYPE (obj))
         {
-        case Lisp_Misc_Buffer_Local_Value:
-          {
-            register struct Lisp_Buffer_Local_Value *ptr
-              = XBUFFER_LOCAL_VALUE (obj);
-            /* If the cdr is nil, avoid recursion for the car.  */
-            if (EQ (ptr->cdr, Qnil))
-              {
-                obj = ptr->realvalue;
-                goto loop;
-              }
-            mark_object (ptr->realvalue);
-            mark_object (ptr->buffer);
-            mark_object (ptr->frame);
-            obj = ptr->cdr;
-            goto loop;
-          }
 
         case Lisp_Misc_Marker:
           /* DO NOT mark thru the marker's chain.
@@ -5633,17 +5642,6 @@ mark_object (arg)
              instead, markers are removed from the chain when freed by gc.  */
           break;
 
-        case Lisp_Misc_Intfwd:
-        case Lisp_Misc_Boolfwd:
-        case Lisp_Misc_Objfwd:
-        case Lisp_Misc_Buffer_Objfwd:
-        case Lisp_Misc_Kboard_Objfwd:
-          /* Don't bother with Lisp_Buffer_Objfwd,
-             since all markable slots in current buffer marked anyway.  */
-          /* Don't need to do Lisp_Objfwd, since the places they point
-             are protected with staticpro.  */
-          break;
-
         case Lisp_Misc_Save_Value:
 #if GC_MARK_STACK
           {
@@ -6048,6 +6046,8 @@ gc_sweep ()
 
             if (!sym->gcmarkbit && !pure_p)
               {
+                if (sym->redirect == SYMBOL_LOCALIZED)
+                  xfree (SYMBOL_BLV (sym));
                 sym->next = symbol_free_list;
                 symbol_free_list = sym;
 #if GC_MARK_STACK