Fix union Lisp_Fwd * alignment bug

It's not portable to cast (e.g.) struct Lisp_Objfwd * to union
Lisp_Fwd * and then back again, because the compiler can then assume
that the pointer is aligned for union Lisp_Fwd * when accessing
the struct Lisp_Objfwd * components, and this assumption might
be incorrect becase we don't force that alignment.
* src/lisp.h (lispfwd): New type, replacing ...
(union Lisp_Fwd): ... this type, which was removed.
All uses changed.
(SET_SYMBOL_FWD): 2nd arg is now void *, not lispfwd.
All uses changed (casts no longer needed; they were
not portable anyway).

1 files changed, 4 insertions, 4 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 7c4691e52c0..c0f7521c9e1 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -1207,7 +1207,7 @@ buffer_local_value (Lisp_Object variable, Lisp_Object buffer)
         result = Fassoc (variable, BVAR (buf, local_var_alist), Qnil);
         if (!NILP (result))
           {
-            if (blv->fwd)
+            if (blv->fwd.fwdptr)
               { /* What binding is loaded right now?  */
                 Lisp_Object current_alist_element = blv->valcell;
 
@@ -1228,7 +1228,7 @@ buffer_local_value (Lisp_Object variable, Lisp_Object buffer)
       }
     case SYMBOL_FORWARDED:
       {
-        union Lisp_Fwd *fwd = SYMBOL_FWD (sym);
+        lispfwd fwd = SYMBOL_FWD (sym);
         if (BUFFER_OBJFWDP (fwd))
           result = per_buffer_value (buf, XBUFFER_OBJFWD (fwd)->offset);
         else
@@ -2140,7 +2140,7 @@ void set_buffer_internal_2 (register struct buffer *b)
           Lisp_Object var = XCAR (XCAR (tail));
           struct Lisp_Symbol *sym = XSYMBOL (var);
           if (sym->u.s.redirect == SYMBOL_LOCALIZED /* Just to be sure.  */
-              && SYMBOL_BLV (sym)->fwd)
+              && SYMBOL_BLV (sym)->fwd.fwdptr)
             /* Just reference the variable
                to cause it to become set for this buffer.  */
             Fsymbol_value (var);
@@ -5444,7 +5444,7 @@ defvar_per_buffer (struct Lisp_Buffer_Objfwd *bo_fwd, const char *namestring,
   bo_fwd->predicate = predicate;
   sym->u.s.declared_special = true;
   sym->u.s.redirect = SYMBOL_FORWARDED;
-  SET_SYMBOL_FWD (sym, (union Lisp_Fwd *) bo_fwd);
+  SET_SYMBOL_FWD (sym, bo_fwd);
   XSETSYMBOL (PER_BUFFER_SYMBOL (offset), sym);
 
   if (PER_BUFFER_IDX (offset) == 0)