(specpdl_ptr): Declare volatile.

(unbind_to): Copy the whole binding and decrement specpdl_ptr
before doing the work of unbinding it.

diff --git a/src/eval.c b/src/eval.c
index 0310e165919806a2e76776be79b057de5e9898b0..cb8bd9d0ffe0c7cbe5d478e18e120782bf51cc65 100644 (file)
--- a/src/eval.c
+++ b/src/eval.c
@@ -117,7 +117,7 @@ struct specbinding *specpdl;
 
 /* Pointer to first unused element in specpdl.  */
 
-struct specbinding *specpdl_ptr;
+volatile struct specbinding *specpdl_ptr;
 
 /* Maximum size allowed for specpdl allocation */
 
@@ -3070,10 +3070,16 @@ unbind_to (count, value)
 
   while (specpdl_ptr != specpdl + count)
     {
-      --specpdl_ptr;
+      /* Copy the binding, and decrement specpdl_ptr, before we do
+        the work to unbind it.  We decrement first
+        so that an error in unbinding won't try to unbind
+        the same entry again, and we copy the binding first
+        in case more bindings are made during some of the code we run.  */
 
-      if (specpdl_ptr->func != 0)
-       (*specpdl_ptr->func) (specpdl_ptr->old_value);
+      struct specbinding this_binding = *--specpdl_ptr;
+
+      if (this_binding.func != 0)
+       (*this_binding.func) (this_binding.old_value);
       /* If the symbol is a list, it is really (SYMBOL WHERE
         . CURRENT-BUFFER) where WHERE is either nil, a buffer, or a
         frame.  If WHERE is a buffer or frame, this indicates we
@@ -3081,29 +3087,29 @@ unbind_to (count, value)
         binding.  WHERE nil means that the variable had the default
         value when it was bound.  CURRENT-BUFFER is the buffer that
          was current when the variable was bound.  */
-      else if (CONSP (specpdl_ptr->symbol))
+      else if (CONSP (this_binding.symbol))
        {
          Lisp_Object symbol, where;
 
-         symbol = XCAR (specpdl_ptr->symbol);
-         where = XCAR (XCDR (specpdl_ptr->symbol));
+         symbol = XCAR (this_binding.symbol);
+         where = XCAR (XCDR (this_binding.symbol));
 
          if (NILP (where))
-           Fset_default (symbol, specpdl_ptr->old_value);
+           Fset_default (symbol, this_binding.old_value);
          else if (BUFFERP (where))
-           set_internal (symbol, specpdl_ptr->old_value, XBUFFER (where), 1);
+           set_internal (symbol, this_binding.old_value, XBUFFER (where), 1);
          else
-           set_internal (symbol, specpdl_ptr->old_value, NULL, 1);
+           set_internal (symbol, this_binding.old_value, NULL, 1);
        }
       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 (!MISCP (SYMBOL_VALUE (specpdl_ptr->symbol)))
-           SET_SYMBOL_VALUE (specpdl_ptr->symbol, specpdl_ptr->old_value);
+         if (!MISCP (SYMBOL_VALUE (this_binding.symbol)))
+           SET_SYMBOL_VALUE (this_binding.symbol, this_binding.old_value);
          else
-           set_internal (specpdl_ptr->symbol, specpdl_ptr->old_value, 0, 1);
+           set_internal (this_binding.symbol, this_binding.old_value, 0, 1);
        }
     }