--- a/libgui/src/main-window.cc	Wed Mar 27 18:37:42 2013 -0400
+++ b/libgui/src/main-window.cc	Wed Mar 27 20:29:06 2013 -0400
@@ -50,6 +50,7 @@
 #include "toplev.h"
 #include "version.h"
 
+#include "cmd-edit.h"
 #include "cmd-hist.h"
 #include "oct-env.h"
 
@@ -1215,22 +1216,35 @@
   Fdbcont ();
 }
 
+// The next three callbacks are invoked by GUI buttons.  Those buttons
+// should only be active when we are doing debugging, which means that
+// Octave is waiting for input in get_debug_input.  Calling
+// command_editor::interrupt will force readline to return even if it
+// has not read any input, and then get_debug_input will return,
+// allowing the evaluator to continue and execute the next statement.
+
 void
 main_window::debug_step_into_callback (void)
 {
   Fdbstep (ovl ("in"));
+
+  command_editor::interrupt (true);
 }
 
 void
 main_window::debug_step_over_callback (void)
 {
   Fdbstep ();
+
+  command_editor::interrupt (true);
 }
 
 void
 main_window::debug_step_out_callback (void)
 {
   Fdbstep (ovl ("out"));
+
+  command_editor::interrupt (true);
 }
 
 void

--- a/libinterp/interpfcn/input.cc	Wed Mar 27 18:37:42 2013 -0400
+++ b/libinterp/interpfcn/input.cc	Wed Mar 27 20:29:06 2013 -0400
@@ -554,15 +554,20 @@
 
       int retval = curr_parser.run ();
 
-      if (retval == 0 && curr_parser.stmt_list)
+      if (command_editor::interrupt (false))
+        break;
+      else
         {
-          curr_parser.stmt_list->accept (*current_evaluator);
+          if (retval == 0 && curr_parser.stmt_list)
+            {
+              curr_parser.stmt_list->accept (*current_evaluator);
 
-          if (octave_completion_matches_called)
-            octave_completion_matches_called = false;
+              if (octave_completion_matches_called)
+                octave_completion_matches_called = false;
+            }
+
+          octave_quit ();
         }
-
-      octave_quit ();
     }
 }
 

--- a/liboctave/util/cmd-edit.cc	Wed Mar 27 18:37:42 2013 -0400
+++ b/liboctave/util/cmd-edit.cc	Wed Mar 27 20:29:06 2013 -0400
@@ -163,6 +163,8 @@
 
   bool do_filename_quoting_desired (bool);
 
+  void do_interrupt (bool);
+
   static int operate_and_get_next (int, int);
 
   static int history_search_backward (int, int);
@@ -587,6 +589,12 @@
   return ::octave_rl_filename_quoting_desired (arg);
 }
 
+void
+gnu_readline::do_interrupt (bool arg)
+{
+  ::octave_rl_done (arg);
+}
+
 int
 gnu_readline::operate_and_get_next (int /* count */, int /* c */)
 {
@@ -1270,6 +1278,26 @@
     ? instance->do_filename_quoting_desired (arg) : false;
 }
 
+bool
+command_editor::interrupt (bool arg)
+{
+  bool retval;
+
+  if (instance_ok ())
+    {
+      // Return the current interrupt state.
+      retval = instance->interrupted;
+
+      instance->do_interrupt (arg);
+
+      instance->interrupted = arg;
+    }
+  else
+    retval = false;
+
+  return retval;
+}
+
 // Return a string which will be printed as a prompt.  The string may
 // contain special characters which are decoded as follows:
 //

--- a/liboctave/util/cmd-edit.h	Wed Mar 27 18:37:42 2013 -0400
+++ b/liboctave/util/cmd-edit.h	Wed Mar 27 20:29:06 2013 -0400
@@ -37,7 +37,7 @@
 protected:
 
   command_editor (void)
-    : command_number (0) { }
+    : command_number (0), interrupted (false) { }
 
 public:
 
@@ -147,6 +147,8 @@
 
   static bool filename_quoting_desired (bool);
 
+  static bool interrupt (bool);
+
   static int current_command_number (void);
 
   static void reset_current_command_number (int n);
@@ -287,6 +289,8 @@
 
   virtual bool do_filename_quoting_desired (bool) { return false; }
 
+  virtual void do_interrupt (bool) { }
+
   int read_octal (const std::string& s);
 
   void error (int);
@@ -295,6 +299,8 @@
 
   // The current command number.
   int command_number;
+
+  bool interrupted;
 };
 
 #endif

--- a/liboctave/util/oct-rl-edit.c	Wed Mar 27 18:37:42 2013 -0400
+++ b/liboctave/util/oct-rl-edit.c	Wed Mar 27 20:29:06 2013 -0400
@@ -218,6 +218,12 @@
   return retval;
 }
 
+void
+octave_rl_done (int arg)
+{
+  rl_done = arg;
+}
+
 char *
 octave_rl_filename_completion_function (const char *text, int state)
 {

--- a/liboctave/util/oct-rl-edit.h	Wed Mar 27 18:37:42 2013 -0400
+++ b/liboctave/util/oct-rl-edit.h	Wed Mar 27 20:29:06 2013 -0400
@@ -90,6 +90,8 @@
 
 extern int octave_rl_filename_quoting_desired (int);
 
+extern void octave_rl_done (int);
+
 extern char *octave_rl_filename_completion_function (const char *, int);
 
 extern void octave_rl_set_basic_word_break_characters (const char *);