Add lisp watchpoints

This allows calling a function whenever a symbol-value is changed.

* src/lisp.h (lisp_h_SYMBOL_TRAPPED_WRITE_P):
(SYMBOL_TRAPPED_WRITE_P): New function/macro.
(lisp_h_SYMBOL_CONSTANT_P): Check for SYMBOL_NOWRITE specifically.
(enum symbol_trapped_write): New enumeration.
(struct Lisp_Symbol): Rename field constant to trapped_write.
(make_symbol_constant): New function.

* src/data.c (Fadd_variable_watcher, Fremove_variable_watcher):
(set_symbol_trapped_write, restore_symbol_trapped_write):
(harmonize_variable_watchers, notify_variable_watchers): New functions.

* src/data.c (Fset_default): Call `notify_variable_watchers' for trapped
symbols.
(set_internal): Change bool argument BIND to 3-value enum and call
`notify_variable_watchers' for trapped symbols.

* src/data.c (syms_of_data):
* src/data.c (syms_of_data):
* src/font.c (syms_of_font):
* src/lread.c (intern_sym, init_obarray):
* src/buffer.c (syms_of_buffer): Use make_symbol_constant.

* src/alloc.c (init_symbol):
* src/bytecode.c (exec_byte_code): Use SYMBOL_TRAPPED_WRITE_P.
* src/data.c (Fmake_variable_buffer_local, Fmake_local_variable):
(Fmake_variable_frame_local):
* src/eval.c (Fdefvaralias, specbind): Refer to Lisp_Symbol's
trapped_write instead of constant.
(Ffuncall): Move subr calling code into separate function.
(funcall_subr): New function.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/bytecode.c b/src/bytecode.c
index be39a81c5e9..868c0148d30 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -569,10 +569,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, Lisp_Object maxdepth,
             if (SYMBOLP (sym)
                 && !EQ (val, Qunbound)
                 && !XSYMBOL (sym)->redirect
-                && !SYMBOL_CONSTANT_P (sym))
+                && !SYMBOL_TRAPPED_WRITE_P (sym))
               SET_SYMBOL_VAL (XSYMBOL (sym), val);
             else
-              set_internal (sym, val, Qnil, false);
+              set_internal (sym, val, Qnil, SET_INTERNAL_SET);
           }
           NEXT;