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, 5 insertions, 4 deletions

diff --git a/src/term.c b/src/term.c
index df7dc9ee464..20f746decdb 100644
--- a/src/term.c
+++ b/src/term.c
@@ -2244,7 +2244,7 @@ set_tty_color_mode (tty, f)
      struct tty_display_info *tty;
      struct frame *f;
 {
-  Lisp_Object tem, val, color_mode_spec;
+  Lisp_Object tem, val;
   Lisp_Object color_mode;
   int mode;
   extern Lisp_Object Qtty_color_mode;
@@ -2256,12 +2256,13 @@ set_tty_color_mode (tty, f)
 
   if (INTEGERP (val))
     color_mode = val;
-  else
+  else if (SYMBOLP (tty_color_mode_alist))
     {
-      tem = (NILP (tty_color_mode_alist) ? Qnil
-             : Fassq (val, XSYMBOL (tty_color_mode_alist)->value));
+      tem = Fassq (val, Fsymbol_value (tty_color_mode_alist));
       color_mode = CONSP (tem) ? XCDR (tem) : Qnil;
     }
+  else
+    color_mode = Qnil;
 
   mode = INTEGERP (color_mode) ? XINT (color_mode) : 0;