Implement debug-on-event

4 files changed, 39 insertions, 3 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 1985cdc3768..04f2e6a5752 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,11 @@
+2011-04-26  Daniel Colascione <dan.colascione@gmail.com>
+
+        * lisp.h (Qdebug): List symbol.
+        * eval.c (Qdebug): restore global linkage.
+        * keyboard.c (debug-on-event): New variable.
+        (handle_user_signal): Break into debugger when debug-on-event
+        matches the current signal symbol.
+
 2011-04-25  Dan Nicolaescu  <dann@ics.uci.edu>
 
         * alloc.c (check_sblock, check_string_bytes)
diff --git a/src/eval.c b/src/eval.c
index d1f327021e6..8716ad78468 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -88,7 +88,7 @@ static Lisp_Object Qdebug_on_error;
 static Lisp_Object Qdeclare;
 Lisp_Object Qinternal_interpreter_environment, Qclosure;
 
-static Lisp_Object Qdebug;
+Lisp_Object Qdebug;
 
 /* This holds either the symbol `run-hooks' or nil.
    It is nil at an early stage of startup, and when Emacs
diff --git a/src/keyboard.c b/src/keyboard.c
index c601649ebca..11cdeaf469c 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -7228,12 +7228,29 @@ handle_user_signal (int sig)
 {
   int old_errno = errno;
   struct user_signal_info *p;
+  const char* special_event_name = NULL;
 
   SIGNAL_THREAD_CHECK (sig);
-
+  
+  if (SYMBOLP (Vdebug_on_event))
+    special_event_name = SDATA (SYMBOL_NAME (Vdebug_on_event));
+  
   for (p = user_signals; p; p = p->next)
     if (p->sig == sig)
       {
+        if (special_event_name &&
+            strcmp (special_event_name, p->name) == 0)
+          {
+            /* Enter the debugger in many ways.  */
+            debug_on_next_call = 1;
+            debug_on_quit = 1;
+            Vquit_flag = Qt;
+            Vinhibit_quit = Qnil;
+
+            /* Eat the event.  */
+            break;
+          }
+        
         p->npending++;
 #ifdef SIGIO
         if (interrupt_input)
@@ -12165,6 +12182,17 @@ text in the region before modifying the buffer.  The next
 `deactivate-mark' call uses this to set the window selection.  */);
   Vsaved_region_selection = Qnil;
 
+  DEFVAR_LISP ("debug-on-event",
+               Vdebug_on_event,
+               doc: /* Enter debugger on this event.  When Emacs
+receives the special event specifed by this variable, it will try to
+break into the debugger as soon as possible instead of processing the
+event normally through `special-event-map'.
+
+Currently, the only supported values for this
+variable are `sigusr1' and `sigusr2'.  */);
+  Vdebug_on_event = intern_c_string ("sigusr2");
+
   /* Create the initial keyboard. */
   initial_kboard = (KBOARD *) xmalloc (sizeof (KBOARD));
   init_kboard (initial_kboard);
diff --git a/src/lisp.h b/src/lisp.h
index 07b2cb0b1ef..44df38e9fa6 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -2796,7 +2796,7 @@ extern void syms_of_lread (void);
 
 /* Defined in eval.c.  */
 extern Lisp_Object Qautoload, Qexit, Qinteractive, Qcommandp, Qdefun, Qmacro;
-extern Lisp_Object Qinhibit_quit, Qclosure;
+extern Lisp_Object Qinhibit_quit, Qclosure, Qdebug;
 extern Lisp_Object Qand_rest;
 extern Lisp_Object Vautoload_queue;
 extern Lisp_Object Vsignaling_function;