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, 14 insertions, 11 deletions

diff --git a/src/buffer.h b/src/buffer.h
index fa3fc6dafb8..b750e490078 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -107,6 +107,11 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #define BUF_BEG(buf) (BEG)
 #define BUF_BEG_BYTE(buf) (BEG_BYTE)
 
+/* !!!FIXME:  all the BUF_BEGV/BUF_ZV/BUF_PT macros are flawed:
+   on indirect (or base) buffers, that value is only correct if that buffer
+   is the current_buffer, or if the buffer's text hasn't been modified (via
+   an indirect buffer) since it was last current.  */
+
 /* Position of beginning of accessible range of buffer.  */
 #define BUF_BEGV(buf) ((buf)->begv)
 #define BUF_BEGV_BYTE(buf) ((buf)->begv_byte)
@@ -313,7 +318,7 @@ while (0)
  - (ptr - (current_buffer)->text->beg <= (unsigned) (GPT_BYTE - BEG_BYTE) ? 0 : GAP_SIZE) \
  + BEG_BYTE)
 
-/* Return character at position POS.  */
+/* Return character at byte position POS.  */
 
 #define FETCH_CHAR(pos)				      	\
   (!NILP (current_buffer->enable_multibyte_characters)	\
@@ -327,7 +332,7 @@ while (0)
 /* Variables used locally in FETCH_MULTIBYTE_CHAR.  */
 extern unsigned char *_fetch_multibyte_char_p;
 
-/* Return character code of multi-byte form at position POS.  If POS
+/* Return character code of multi-byte form at byte position POS.  If POS
    doesn't point the head of valid multi-byte form, only the byte at
    POS is returned.  No range checking.  */
 
@@ -336,7 +341,7 @@ extern unsigned char *_fetch_multibyte_char_p;
 			       + (pos) + BEG_ADDR - BEG_BYTE),	 	\
    STRING_CHAR (_fetch_multibyte_char_p))
 
-/* Return character at position POS.  If the current buffer is unibyte
+/* Return character at byte position POS.  If the current buffer is unibyte
    and the character is not ASCII, make the returning character
    multibyte.  */
 
@@ -447,7 +452,10 @@ struct buffer_text
     /* The markers that refer to this buffer.
        This is actually a single marker ---
        successive elements in its marker `chain'
-       are the other markers referring to this buffer.  */
+       are the other markers referring to this buffer.
+       This is a singly linked unordered list, which means that it's
+       very cheap to add a marker to the list and it's also very cheap
+       to move a marker within a buffer.  */
     struct Lisp_Marker *markers;
 
     /* Usually 0.  Temporarily set to 1 in decode_coding_gap to
@@ -843,6 +851,7 @@ extern struct buffer buffer_defaults;
    be a Lisp-level local variable for the slot, it has no default value,
    and the corresponding slot in buffer_defaults is not used.  */
 
+
 extern struct buffer buffer_local_flags;
 
 /* For each buffer slot, this points to the Lisp symbol name
@@ -948,7 +957,7 @@ extern int last_per_buffer_idx;
    from the start of a buffer structure.  */
 
 #define PER_BUFFER_VAR_OFFSET(VAR) \
-    ((char *) &buffer_local_flags.VAR - (char *) &buffer_local_flags)
+  ((char *) &((struct buffer *)0)->VAR - (char *) ((struct buffer *)0))
 
 /* Return the index of buffer-local variable VAR.  Each per-buffer
    variable has an index > 0 associated with it, except when it always
@@ -1013,11 +1022,5 @@ extern int last_per_buffer_idx;
 #define PER_BUFFER_VALUE(BUFFER, OFFSET) \
       (*(Lisp_Object *)((OFFSET) + (char *) (BUFFER)))
 
-/* Return the symbol of the per-buffer variable at offset OFFSET in
-   the buffer structure.  */
-
-#define PER_BUFFER_SYMBOL(OFFSET) \
-      (*(Lisp_Object *)((OFFSET) + (char *) &buffer_local_symbols))
-
 /* arch-tag: 679305dd-d41c-4a50-b170-3caf5c97b2d1
    (do not change this comment) */