--- a/doc/interpreter/debug.txi	Fri Nov 15 20:58:50 2002 +0000
+++ b/doc/interpreter/debug.txi	Fri Nov 15 23:22:27 2002 +0000
@@ -15,6 +15,8 @@
 
 @DOCSTRING(dbtype)
 
-@DOCSTRING(debug_on_error)
+@DOCSTRING(debug_on_interrupt)
 
 @DOCSTRING(debug_on_warning)
+
+@DOCSTRING(debug_on_error)

--- a/src/ChangeLog	Fri Nov 15 20:58:50 2002 +0000
+++ b/src/ChangeLog	Fri Nov 15 23:22:27 2002 +0000
@@ -1,5 +1,14 @@
 2002-11-15  John W. Eaton  <jwe@bevo.che.wisc.edu>
 
+	* pt-bp.cc (octave_debug_on_interrupt_state): New global variable.
+	* pt-bp.h: Provide decl.
+	(MAYBE_DO_BREAKPOINT): Check it.
+
+	* sighandlers.cc (sigint_handler): Handle debug_on_interrupt.
+	(Vdebug_on_interrupt): New static variable.
+	(symbols_of_sighandlers): New function.  DEFVAR Vdebug_on_interrupt.
+	(debug_on_interrupt): New function.
+
 	* lex.h (YY_FATAL_ERROR): Use OCTAVE_QUIT here.
 
 	* utils.cc (toplevel): Delete variable.

--- a/src/pt-bp.cc	Fri Nov 15 20:58:50 2002 +0000
+++ b/src/pt-bp.cc	Fri Nov 15 23:22:27 2002 +0000
@@ -33,6 +33,10 @@
 #include "pager.h"
 #include "pt-all.h"
 
+// TRUE means SIGINT should put us in the debugger at the next
+// available breakpoint.
+bool octave_debug_on_interrupt_state = false;
+
 void 
 tree_breakpoint::take_action (tree &tr)
 {

--- a/src/pt-bp.h	Fri Nov 15 20:58:50 2002 +0000
+++ b/src/pt-bp.h	Fri Nov 15 23:22:27 2002 +0000
@@ -168,15 +168,22 @@
   tree_breakpoint& operator = (const tree_breakpoint&);
 };
 
+// TRUE means SIGINT should put us in the debugger at the next
+// available breakpoint.
+extern bool octave_debug_on_interrupt_state;
+
 #define MAYBE_DO_BREAKPOINT \
   do \
     { \
-      if ((tree::break_next && tree::last_line == 0) \
+      if (octave_debug_on_interrupt_state \
+	  || (tree::break_next && tree::last_line == 0) \
 	  || (tree::break_next \
 	      && curr_function == tree::break_function \
 	      && tree::last_line != line ()) \
 	  || is_breakpoint ()) \
         { \
+          octave_debug_on_interrupt_state = false; \
+ \
           tree::break_next = false; \
  \
           if (curr_function) \

--- a/src/sighandlers.cc	Fri Nov 15 20:58:50 2002 +0000
+++ b/src/sighandlers.cc	Fri Nov 15 23:22:27 2002 +0000
@@ -39,9 +39,11 @@
 #include "cmd-edit.h"
 #include "quit.h"
 
+#include "defun.h"
 #include "error.h"
 #include "load-save.h"
 #include "pager.h"
+#include "pt-bp.h"
 #include "sighandlers.h"
 #include "syswait.h"
 #include "toplev.h"
@@ -54,6 +56,9 @@
 // TRUE means we can be interrupted.
 bool can_interrupt = false;
 
+// TRUE means we should try to enter the debugger on SIGINT.
+static bool Vdebug_on_interrupt = false;
+
 #if RETSIGTYPE == void
 #define SIGHANDLER_RETURN(status) return
 #else
@@ -266,15 +271,23 @@
 
   if (can_interrupt)
     {
-#if defined (USE_EXCEPTIONS_FOR_INTERRUPTS)
+      if (Vdebug_on_interrupt)
+	{
+	  if (! octave_debug_on_interrupt_state)
+	    {
+	      octave_debug_on_interrupt_state = true;
+
+	      SIGHANDLER_RETURN (0);
+	    }
+	  else
+	    // Clear the flag and do normal interrupt stuff.
+	    octave_debug_on_interrupt_state = false;
+	}
+
       octave_interrupt_state = 1;
 
       if (octave_interrupt_immediately)
 	octave_jump_to_enclosing_context ();
-#else
-      octave_interrupt_state = 1;
-      panic_impossible ();
-#endif
     }
 
   SIGHANDLER_RETURN (0);
@@ -601,6 +614,28 @@
     return foo;
 }
 
+static int
+debug_on_interrupt (void)
+{
+  Vdebug_on_interrupt = check_preference ("debug_on_interrupt");
+
+  return 0;
+}
+
+void
+symbols_of_sighandlers (void)
+{
+  DEFVAR (debug_on_interrupt, 0.0, debug_on_interrupt,
+    "-*- texinfo -*-\n\
+@defvr {Built-in Variable} debug_on_interrupt\n\
+If @code{debug_on_interrupt} is nonzero, Octave will try to enter\n\
+debugging mode when it receives an interrupt signal (typically\n\
+generated with @kbd{C-c}).  If a second interrupt signal is received\n\
+before reaching the debugging mode, a normal interrupt will occur.\n\
+The default value is 0.\n\
+@end defvr");
+}
+
 /*
 ;;; Local Variables: ***
 ;;; mode: C++ ***