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, 47 insertions, 47 deletions

diff --git a/src/lread.c b/src/lread.c
index 83ebc8b3b10..a04b9679d83 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -3687,7 +3687,8 @@ it defaults to the value of `obarray'.  */)
       && EQ (obarray, initial_obarray))
     {
       XSYMBOL (sym)->constant = 1;
-      XSYMBOL (sym)->value = sym;
+      XSYMBOL (sym)->redirect = SYMBOL_PLAINVAL;
+      SET_SYMBOL_VAL (XSYMBOL (sym), sym);
     }
 
   ptr = &XVECTOR (obarray)->contents[XINT (tem)];
@@ -3768,8 +3769,6 @@ OBARRAY defaults to the value of the variable `obarray'.  */)
        error ("Attempt to unintern t or nil"); */
 
   XSYMBOL (tem)->interned = SYMBOL_UNINTERNED;
-  XSYMBOL (tem)->constant = 0;
-  XSYMBOL (tem)->indirect_variable = 0;
 
   hash = oblookup_last_bucket_number;
 
@@ -3914,35 +3913,31 @@ void
 init_obarray ()
 {
   Lisp_Object oblength;
-  int hash;
-  Lisp_Object *tem;
 
   XSETFASTINT (oblength, OBARRAY_SIZE);
 
-  Qnil = Fmake_symbol (make_pure_c_string ("nil"));
   Vobarray = Fmake_vector (oblength, make_number (0));
   initial_obarray = Vobarray;
   staticpro (&initial_obarray);
-  /* Intern nil in the obarray */
-  XSYMBOL (Qnil)->interned = SYMBOL_INTERNED_IN_INITIAL_OBARRAY;
-  XSYMBOL (Qnil)->constant = 1;
-
-  /* These locals are to kludge around a pyramid compiler bug. */
-  hash = hash_string ("nil", 3);
-  /* Separate statement here to avoid VAXC bug. */
-  hash %= OBARRAY_SIZE;
-  tem = &XVECTOR (Vobarray)->contents[hash];
-  *tem = Qnil;
 
   Qunbound = Fmake_symbol (make_pure_c_string ("unbound"));
-  XSYMBOL (Qnil)->function = Qunbound;
-  XSYMBOL (Qunbound)->value = Qunbound;
+  /* Set temporary dummy values to Qnil and Vpurify_flag to satisfy the
+     NILP (Vpurify_flag) check in intern_c_string.  */
+  Qnil = make_number (-1); Vpurify_flag = make_number (1);
+  Qnil = intern_c_string ("nil");
+
+  /* Fmake_symbol inits fields of new symbols with Qunbound and Qnil,
+     so those two need to be fixed manally.  */
+  SET_SYMBOL_VAL (XSYMBOL (Qunbound), Qunbound);
   XSYMBOL (Qunbound)->function = Qunbound;
+  XSYMBOL (Qunbound)->plist = Qnil;
+  /* XSYMBOL (Qnil)->function = Qunbound; */
+  SET_SYMBOL_VAL (XSYMBOL (Qnil), Qnil);
+  XSYMBOL (Qnil)->constant = 1;
+  XSYMBOL (Qnil)->plist = Qnil;
 
   Qt = intern_c_string ("t");
-  XSYMBOL (Qnil)->value = Qnil;
-  XSYMBOL (Qnil)->plist = Qnil;
-  XSYMBOL (Qt)->value = Qt;
+  SET_SYMBOL_VAL (XSYMBOL (Qt), Qt);
   XSYMBOL (Qt)->constant = 1;
 
   /* Qt is correct even if CANNOT_DUMP.  loadup.el will set to nil at end.  */
@@ -3981,27 +3976,29 @@ defalias (sname, string)
    to a C variable of type int.  Sample call:
    DEFVAR_INT ("emacs-priority", &emacs_priority, "Documentation");  */
 void
-defvar_int (const char *namestring, EMACS_INT *address)
+defvar_int (struct Lisp_Intfwd *i_fwd,
+            const char *namestring, EMACS_INT *address)
 {
-  Lisp_Object sym, val;
+  Lisp_Object sym;
   sym = intern_c_string (namestring);
-  val = allocate_misc ();
-  XMISCTYPE (val) = Lisp_Misc_Intfwd;
-  XINTFWD (val)->intvar = address;
-  SET_SYMBOL_VALUE (sym, val);
+  i_fwd->type = Lisp_Fwd_Int;
+  i_fwd->intvar = address;
+  XSYMBOL (sym)->redirect = SYMBOL_FORWARDED;
+  SET_SYMBOL_FWD (XSYMBOL (sym), (union Lisp_Fwd *)i_fwd);
 }
 
 /* Similar but define a variable whose value is t if address contains 1,
    nil if address contains 0.  */
 void
-defvar_bool (const char *namestring, int *address)
+defvar_bool (struct Lisp_Boolfwd *b_fwd,
+             const char *namestring, int *address)
 {
-  Lisp_Object sym, val;
+  Lisp_Object sym;
   sym = intern_c_string (namestring);
-  val = allocate_misc ();
-  XMISCTYPE (val) = Lisp_Misc_Boolfwd;
-  XBOOLFWD (val)->boolvar = address;
-  SET_SYMBOL_VALUE (sym, val);
+  b_fwd->type = Lisp_Fwd_Bool;
+  b_fwd->boolvar = address;
+  XSYMBOL (sym)->redirect = SYMBOL_FORWARDED;
+  SET_SYMBOL_FWD (XSYMBOL (sym), (union Lisp_Fwd *)b_fwd);
   Vbyte_boolean_vars = Fcons (sym, Vbyte_boolean_vars);
 }
 
@@ -4011,20 +4008,22 @@ defvar_bool (const char *namestring, int *address)
    gc-marked for some other reason, since marking the same slot twice
    can cause trouble with strings.  */
 void
-defvar_lisp_nopro (const char *namestring, Lisp_Object *address)
+defvar_lisp_nopro (struct Lisp_Objfwd *o_fwd,
+                   const char *namestring, Lisp_Object *address)
 {
-  Lisp_Object sym, val;
+  Lisp_Object sym;
   sym = intern_c_string (namestring);
-  val = allocate_misc ();
-  XMISCTYPE (val) = Lisp_Misc_Objfwd;
-  XOBJFWD (val)->objvar = address;
-  SET_SYMBOL_VALUE (sym, val);
+  o_fwd->type = Lisp_Fwd_Obj;
+  o_fwd->objvar = address;
+  XSYMBOL (sym)->redirect = SYMBOL_FORWARDED;
+  SET_SYMBOL_FWD (XSYMBOL (sym), (union Lisp_Fwd *)o_fwd);
 }
 
 void
-defvar_lisp (const char *namestring, Lisp_Object *address)
+defvar_lisp (struct Lisp_Objfwd *o_fwd,
+             const char *namestring, Lisp_Object *address)
 {
-  defvar_lisp_nopro (namestring, address);
+  defvar_lisp_nopro (o_fwd, namestring, address);
   staticpro (address);
 }
 
@@ -4032,14 +4031,15 @@ defvar_lisp (const char *namestring, Lisp_Object *address)
    at a particular offset in the current kboard object.  */
 
 void
-defvar_kboard (const char *namestring, int offset)
+defvar_kboard (struct Lisp_Kboard_Objfwd *ko_fwd,
+               const char *namestring, int offset)
 {
-  Lisp_Object sym, val;
+  Lisp_Object sym;
   sym = intern_c_string (namestring);
-  val = allocate_misc ();
-  XMISCTYPE (val) = Lisp_Misc_Kboard_Objfwd;
-  XKBOARD_OBJFWD (val)->offset = offset;
-  SET_SYMBOL_VALUE (sym, val);
+  ko_fwd->type = Lisp_Fwd_Kboard_Obj;
+  ko_fwd->offset = offset;
+  XSYMBOL (sym)->redirect = SYMBOL_FORWARDED;
+  SET_SYMBOL_FWD (XSYMBOL (sym), (union Lisp_Fwd *)ko_fwd);
 }
 
 /* Record the value of load-path used at the start of dumping