Make defvar affect the default binding outside of any let.

* src/eval.c (default_toplevel_binding): New function.
(Fdefvar): Use it.
(unbind_to, backtrace_eval_unrewind): Do a bit of CSE simplification.
(Fdefault_toplevel_value, Fset_default_toplevel_value): New subrs.
(syms_of_eval): Export them.
* src/data.c (Fdefault_value): Micro cleanup.
* src/term.c (init_tty): Use "false".
* lisp/custom.el (custom-initialize-default, custom-initialize-set)
(custom-initialize-reset, custom-initialize-changed): Affect the
toplevel-default-value (bug#6275, bug#14586).
* lisp/emacs-lisp/advice.el (ad-compile-function): Undo previous workaround
for bug#6275.
* test/automated/core-elisp-tests.el: New file.

1 files changed, 82 insertions, 42 deletions

diff --git a/src/eval.c b/src/eval.c
index cb716690e3c..8ee259110f4 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -658,6 +658,51 @@ The return value is BASE-VARIABLE.  */)
   return base_variable;
 }
 
+static union specbinding *
+default_toplevel_binding (Lisp_Object symbol)
+{
+  union specbinding *binding = NULL;
+  union specbinding *pdl = specpdl_ptr;
+  while (pdl > specpdl)
+    {
+      switch ((--pdl)->kind)
+        {
+        case SPECPDL_LET_DEFAULT:
+        case SPECPDL_LET:
+          if (EQ (specpdl_symbol (pdl), symbol))
+            binding = pdl;
+          break;
+        }
+    }
+  return binding;
+}
+
+DEFUN ("default-toplevel-value", Fdefault_toplevel_value, Sdefault_toplevel_value, 1, 1, 0,
+       doc: /* Return SYMBOL's toplevel default value.
+"Toplevel" means outside of any let binding.  */)
+  (Lisp_Object symbol)
+{
+  union specbinding *binding = default_toplevel_binding (symbol);
+  Lisp_Object value
+    = binding ? specpdl_old_value (binding) : Fdefault_value (symbol);
+  if (!EQ (value, Qunbound))
+    return value;
+  xsignal1 (Qvoid_variable, symbol);
+}
+
+DEFUN ("set-default-toplevel-value", Fset_default_toplevel_value,
+       Sset_default_toplevel_value, 2, 2, 0,
+       doc: /* Set SYMBOL's toplevel default value to VALUE.
+"Toplevel" means outside of any let binding.  */)
+     (Lisp_Object symbol, Lisp_Object value)
+{
+  union specbinding *binding = default_toplevel_binding (symbol);
+  if (binding)
+    set_specpdl_old_value (binding, value);
+  else
+    Fset_default (symbol, value);
+  return Qnil;
+}
 
 DEFUN ("defvar", Fdefvar, Sdefvar, 1, UNEVALLED, 0,
        doc: /* Define SYMBOL as a variable, and return SYMBOL.
@@ -706,18 +751,10 @@ usage: (defvar SYMBOL &optional INITVALUE DOCSTRING)  */)
       else
         { /* Check if there is really a global binding rather than just a let
              binding that shadows the global unboundness of the var.  */
-          union specbinding *pdl = specpdl_ptr;
-          while (pdl > specpdl)
+          union specbinding *binding = default_toplevel_binding (sym);
+          if (binding && EQ (specpdl_old_value (binding), Qunbound))
             {
-              if ((--pdl)->kind >= SPECPDL_LET
-                  && EQ (specpdl_symbol (pdl), sym)
-                  && EQ (specpdl_old_value (pdl), Qunbound))
-                {
-                  message_with_string
-                    ("Warning: defvar ignored because %s is let-bound",
-                     SYMBOL_NAME (sym), 1);
-                  break;
-                }
+              set_specpdl_old_value (binding, eval_sub (XCAR (tail)));
             }
         }
       tail = XCDR (tail);
@@ -3311,19 +3348,21 @@ unbind_to (ptrdiff_t count, Lisp_Object value)
         case SPECPDL_BACKTRACE:
           break;
         case SPECPDL_LET:
-          /* If variable has a trivial value (no forwarding), we can
-             just set it.  No need to check for constant symbols here,
-             since that was already done by specbind.  */
-          if (XSYMBOL (specpdl_symbol (specpdl_ptr))->redirect
-              == SYMBOL_PLAINVAL)
-            SET_SYMBOL_VAL (XSYMBOL (specpdl_symbol (specpdl_ptr)),
-                            specpdl_old_value (specpdl_ptr));
-          else
-            /* NOTE: we only ever come here if make_local_foo was used for
-               the first time on this var within this let.  */
-            Fset_default (specpdl_symbol (specpdl_ptr),
-                          specpdl_old_value (specpdl_ptr));
-          break;
+          { /* If variable has a trivial value (no forwarding), we can
+               just set it.  No need to check for constant symbols here,
+               since that was already done by specbind.  */
+            struct Lisp_Symbol *sym = XSYMBOL (specpdl_symbol (specpdl_ptr));
+            if (sym->redirect == SYMBOL_PLAINVAL)
+              {
+                SET_SYMBOL_VAL (sym, specpdl_old_value (specpdl_ptr));
+                break;
+              }
+            else
+              { /* FALLTHROUGH!!
+                   NOTE: we only ever come here if make_local_foo was used for
+                   the first time on this var within this let.  */
+              }
+          }
         case SPECPDL_LET_DEFAULT:
           Fset_default (specpdl_symbol (specpdl_ptr),
                         specpdl_old_value (specpdl_ptr));
@@ -3511,24 +3550,23 @@ backtrace_eval_unrewind (int distance)
         case SPECPDL_BACKTRACE:
           break;
         case SPECPDL_LET:
-          /* If variable has a trivial value (no forwarding), we can
-             just set it.  No need to check for constant symbols here,
-             since that was already done by specbind.  */
-          if (XSYMBOL (specpdl_symbol (tmp))->redirect
-              == SYMBOL_PLAINVAL)
-            {
-              struct Lisp_Symbol *sym = XSYMBOL (specpdl_symbol (tmp));
-              Lisp_Object old_value = specpdl_old_value (tmp);
-              set_specpdl_old_value (tmp, SYMBOL_VAL (sym));
-              SET_SYMBOL_VAL (sym, old_value);
-              break;
-            }
-          else
-            {
-              /* FALLTHROUGH!
-                 NOTE: we only ever come here if make_local_foo was used for
-                 the first time on this var within this let.  */
-            }
+          { /* If variable has a trivial value (no forwarding), we can
+               just set it.  No need to check for constant symbols here,
+               since that was already done by specbind.  */
+            struct Lisp_Symbol *sym = XSYMBOL (specpdl_symbol (tmp));
+            if (sym->redirect == SYMBOL_PLAINVAL)
+              {
+                Lisp_Object old_value = specpdl_old_value (tmp);
+                set_specpdl_old_value (tmp, SYMBOL_VAL (sym));
+                SET_SYMBOL_VAL (sym, old_value);
+                break;
+              }
+            else
+              { /* FALLTHROUGH!!
+                   NOTE: we only ever come here if make_local_foo was used for
+                   the first time on this var within this let.  */
+              }
+          }
         case SPECPDL_LET_DEFAULT:
           {
             Lisp_Object sym = specpdl_symbol (tmp);
@@ -3796,6 +3834,8 @@ alist of active lexical bindings.  */);
   defsubr (&Ssetq);
   defsubr (&Squote);
   defsubr (&Sfunction);
+  defsubr (&Sdefault_toplevel_value);
+  defsubr (&Sset_default_toplevel_value);
   defsubr (&Sdefvar);
   defsubr (&Sdefvaralias);
   defsubr (&Sdefconst);