Introduce an enum Lisp_Fwd_Predicate

Using an enum instead of a symbol makes it obvious that this field is
of no concern to the GC.

* src/lisp.h (enum Lisp_Fwd_Predicate): New.
(struct Lisp_Fwd): Use it instead of a symbol.
* src/buffer.c (DEFVAR_PER_BUFFER): Create the necessary enum constant
instead of a symbol.
* src/data.c (check_fwd_predicate, check_choice): New helpers.
(store_symval_forwarding): Use it.

1 files changed, 9 insertions, 13 deletions

diff --git a/src/buffer.c b/src/buffer.c
index ae5016df50e..39b5e29067a 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -5017,19 +5017,15 @@ init_buffer (void)
    that nil is allowed too).  DOC is a dummy where you write the doc
    string as a comment.  */
 
-/* FIXME: use LISPSYM_INITIALLY instead of TAG_PTR_INITIALLY */
-#define DEFVAR_PER_BUFFER(lname, vname, predicate_, doc)                \
-  do {                                                                  \
-    const Lisp_Object sym                                               \
-      = TAG_PTR_INITIALLY (Lisp_Symbol, (intptr_t)((i##predicate_)      \
-                                                   * sizeof *lispsym)); \
-    static const struct Lisp_Fwd bo_fwd                                 \
-        = { .type = Lisp_Fwd_Buffer_Obj,                                \
-            .bufoffset = offsetof (struct buffer, vname##_),            \
-            .u.bufpredicate = sym };                                    \
-    static_assert (offsetof (struct buffer, vname##_)                   \
-                   < (1 << 8 * sizeof bo_fwd.bufoffset));               \
-    defvar_per_buffer (&bo_fwd, lname);                                 \
+#define DEFVAR_PER_BUFFER(lname, vname, predicate, doc)         \
+  do {                                                          \
+    static const struct Lisp_Fwd bo_fwd                         \
+        = { .type = Lisp_Fwd_Buffer_Obj,                        \
+            .bufoffset = offsetof (struct buffer, vname##_),    \
+            .u.bufpredicate = FWDPRED_##predicate };            \
+    static_assert (offsetof (struct buffer, vname##_)           \
+                   < (1 << 8 * sizeof bo_fwd.bufoffset));       \
+    defvar_per_buffer (&bo_fwd, lname);                         \
   } while (0)
 
 static void