Try and fix unbind_to when localness of binding has changed

* eval.c (unbind_to): Don't unbind a local binding into the global
binding when the local binding disappeared.  Inversely, don't unbind
a global binding into a newly created local binding.
* data.c (set_internal): Make its `buf' arg into a `where' arg so we
can specify the frame to use, when applicable.  Adjust callers.

src/ChangeLog

+2010-05-07  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+	* eval.c (unbind_to): Don't unbind a local binding into the global
+	binding when the local binding disappeared.  Inversely, don't unbind
+	a global binding into a newly created local binding.
+	* data.c (set_internal): Make its `buf' arg into a `where' arg so we
+	can specify the frame to use, when applicable.  Adjust callers.
+
 2010-05-07  Vincent Belaïche  <vincent.belaiche@gmail.com>
             Stefan Monnier  <monnier@iro.umontreal.ca>

src/bytecode.c

@@ -604,7 +604,7 @@ If the third argument is incorrect, Emacs may crash.  */)
 	    else
 	      {
 		BEFORE_POTENTIAL_GC ();
-		set_internal (sym, val, current_buffer, 0);
+		set_internal (sym, val, Qnil, 0);
 		AFTER_POTENTIAL_GC ();
 	      }
 	  }

src/data.c

@@ -1156,7 +1156,7 @@ DEFUN ("set", Fset, Sset, 2, 2, 0,
      (symbol, newval)
      register Lisp_Object symbol, newval;
 {
-  set_internal (symbol, newval, current_buffer, 0);
+  set_internal (symbol, newval, Qnil, 0);
   return newval;
 }
 
@@ -1196,29 +1196,25 @@ let_shadows_global_binding_p (symbol)
 }
 
 /* Store the value NEWVAL into SYMBOL.
-   If buffer-locality is an issue, BUF specifies which buffer to use.
-   (0 stands for the current buffer.)
+   If buffer/frame-locality is an issue, WHERE specifies which context to use.
+   (nil stands for the current buffer/frame).
 
    If BINDFLAG is zero, then if this symbol is supposed to become
    local in every buffer where it is set, then we make it local.
    If BINDFLAG is nonzero, we don't do that.  */
 
 void
-set_internal (symbol, newval, buf, bindflag)
-     register Lisp_Object symbol, newval;
-     struct buffer *buf;
+set_internal (symbol, newval, where, bindflag)
+     register Lisp_Object symbol, newval, where;
      int bindflag;
 {
   int voide = EQ (newval, Qunbound);
   struct Lisp_Symbol *sym;
   Lisp_Object tem1;
 
-  if (buf == 0)
-    buf = current_buffer;
-
   /* If restoring in a dead buffer, do nothing.  */
-  if (NILP (buf->name))
-    return;
+  /* if (BUFFERP (where) && NILP (XBUFFER (where)->name))
+      return; */
 
   CHECK_SYMBOL (symbol);
   if (SYMBOL_CONSTANT_P (symbol))
@@ -1241,15 +1237,19 @@ set_internal (symbol, newval, buf, bindflag)
     case SYMBOL_LOCALIZED:
       {
 	struct Lisp_Buffer_Local_Value *blv = SYMBOL_BLV (sym);
-	Lisp_Object tmp; XSETBUFFER (tmp, buf);
-
+	if (NILP (where))
+	  {
+	    if (blv->frame_local)
+	      where = selected_frame;
+	    else
+	      XSETBUFFER (where, current_buffer);
+	  }
 	/* If the current buffer is not the buffer whose binding is
 	   loaded, or if there may be frame-local bindings and the frame
 	   isn't the right one, or if it's a Lisp_Buffer_Local_Value and
 	   the default binding is loaded, the loaded binding may be the
 	   wrong one.  */
-	if (!EQ (blv->where,
-		 blv->frame_local ? selected_frame : tmp)
+	if (!EQ (blv->where, where)
 	    /* Also unload a global binding (if the var is local_if_set). */
 	    || (EQ (blv->valcell, blv->defcell)))
 	  {
@@ -1261,19 +1261,12 @@ set_internal (symbol, newval, buf, bindflag)
 	      SET_BLV_VALUE (blv, do_symval_forwarding (blv->fwd));
 
 	    /* Find the new binding.  */
-	    {
-	      XSETSYMBOL (symbol, sym); /* May have changed via aliasing.  */
-	      if (blv->frame_local)
-		{
-		  tem1 = Fassq (symbol, XFRAME (selected_frame)->param_alist);
-		  blv->where = selected_frame;
-		}
-	      else
-		{
-		  tem1 = Fassq (symbol, buf->local_var_alist);
-		  blv->where = tmp;
-		}
-	    }
+	    XSETSYMBOL (symbol, sym); /* May have changed via aliasing.  */
+	    tem1 = Fassq (symbol,
+			  (blv->frame_local
+			   ? XFRAME (where)->param_alist
+			   : XBUFFER (where)->local_var_alist));
+	    blv->where = where;
 	    blv->found = 1;
 
 	    if (NILP (tem1))
@@ -1303,8 +1296,8 @@ set_internal (symbol, newval, buf, bindflag)
 		       bindings, not for frame-local bindings.  */
 		    eassert (!blv->frame_local);
 		    tem1 = Fcons (symbol, XCDR (blv->defcell));
-		    buf->local_var_alist
-		      = Fcons (tem1, buf->local_var_alist);
+		    XBUFFER (where)->local_var_alist
+		      = Fcons (tem1, XBUFFER (where)->local_var_alist);
 		  }
 	      }
 
@@ -1322,12 +1315,16 @@ set_internal (symbol, newval, buf, bindflag)
 		 buffer-local indicator, not through Lisp_Objfwd, etc.  */
 	      blv->fwd = NULL;
 	    else
-	      store_symval_forwarding (blv->fwd, newval, buf);
+	      store_symval_forwarding (blv->fwd, newval,
+				       BUFFERP (where)
+				       ? XBUFFER (where) : current_buffer);
 	  }
 	break;
       }
     case SYMBOL_FORWARDED:
       {
+	struct buffer *buf
+	  = BUFFERP (where) ? XBUFFER (where) : current_buffer;
 	union Lisp_Fwd *innercontents = SYMBOL_FWD (sym);
 	if (BUFFER_OBJFWDP (innercontents))
 	  {

src/eval.c

@@ -26,6 +26,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "commands.h"
 #include "keyboard.h"
 #include "dispextern.h"
+#include "frame.h"		/* For XFRAME.  */
 
 #if HAVE_X_WINDOWS
 #include "xterm.h"
@@ -786,7 +787,7 @@ The return value is BASE-VARIABLE.  */)
      so that old-code that affects n_a before the aliasing is setup
      still works.  */
   if (NILP (Fboundp (base_variable)))
-    set_internal (base_variable, find_symbol_value (new_alias), NULL, 1);
+    set_internal (base_variable, find_symbol_value (new_alias), Qnil, 1);
 
   {
     struct specbinding *p;
@@ -3335,7 +3336,7 @@ specbind (symbol, value)
 	  if (!sym->constant)
 	    SET_SYMBOL_VAL (sym, value);
 	  else
-	    set_internal (symbol, value, 0, 1);
+	    set_internal (symbol, value, Qnil, 1);
 	  break;
 	}
     case SYMBOL_LOCALIZED: case SYMBOL_FORWARDED:
@@ -3395,7 +3396,7 @@ specbind (symbol, value)
 	  specpdl_ptr->symbol = symbol;
 
 	specpdl_ptr++;
-	set_internal (symbol, value, 0, 1);
+	set_internal (symbol, value, Qnil, 1);
 	break;
       }
     default: abort ();
@@ -3457,27 +3458,26 @@ unbind_to (count, value)
 
 	  if (NILP (where))
 	    Fset_default (symbol, this_binding.old_value);
+	  /* If `where' is non-nil, reset the value in the appropriate
+	     local binding, but only if that binding still exists.  */
 	  else if (BUFFERP (where))
-	    if (!NILP (Flocal_variable_p (symbol, where)))
-	      set_internal (symbol, this_binding.old_value, XBUFFER (where), 1);
-	    /* else if (!NILP (Fbuffer_live_p (where)))
-	      error ("Unbinding local %s to global!", symbol); */
-            else
-              ;
-	  else
-	    set_internal (symbol, this_binding.old_value, NULL, 1);
+	    {
+	      if (BUFFERP (where)
+		  ? !NILP (Flocal_variable_p (symbol, where))
+		  : !NILP (Fassq (symbol, XFRAME (where)->param_alist)))
+		set_internal (symbol, this_binding.old_value, where, 1);
+	    }
 	}
+      /* 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.  */
+      else if (XSYMBOL (this_binding.symbol)->redirect == SYMBOL_PLAINVAL)
+	SET_SYMBOL_VAL (XSYMBOL (this_binding.symbol),
+			this_binding.old_value);
       else
-	{
-	  /* 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 (this_binding.symbol)->redirect == SYMBOL_PLAINVAL)
-	    SET_SYMBOL_VAL (XSYMBOL (this_binding.symbol),
-			    this_binding.old_value);
-	  else
-	    set_internal (this_binding.symbol, this_binding.old_value, 0, 1);
-	}
+	/* NOTE: we only ever come here if make_local_foo was used for
+	   the first time on this var within this let.  */
+	Fset_default (this_binding.symbol, this_binding.old_value);
     }
 
   if (NILP (Vquit_flag) && !NILP (quitf))

src/lisp.h

@@ -2381,7 +2381,7 @@ extern void args_out_of_range_3 P_ ((Lisp_Object, Lisp_Object,
 				     Lisp_Object)) NO_RETURN;
 extern Lisp_Object wrong_type_argument P_ ((Lisp_Object, Lisp_Object)) NO_RETURN;
 extern Lisp_Object do_symval_forwarding (union Lisp_Fwd *);
-extern void set_internal (Lisp_Object, Lisp_Object, struct buffer *, int);
+extern void set_internal (Lisp_Object, Lisp_Object, Lisp_Object, int);
 extern void syms_of_data P_ ((void));
 extern void init_data P_ ((void));
 extern void swap_in_global_binding P_ ((struct Lisp_Symbol *));