gdb: Add support for detecting deleted breakpoints

Added a python event listener that prints a message whenever a
breakpoint is deleted.

The regexp for detecting deleted breakpoints is now applied repeatedly
as long as there are additional matches as the gdb listener writes
one message for each deleted breakpoint.

This should fix realgud#278, realgud#180 and realgud#61.

realgud/common/track.el

@@ -658,22 +658,27 @@ of the breakpoints found in command buffer."
       (let* ((loc-pat (realgud-cmdbuf-pat "brkpt-del")))
         (when loc-pat
           (let ((bp-num-group (realgud-loc-pat-num loc-pat))
-                (loc-regexp   (realgud-loc-pat-regexp loc-pat)))
-            (when (and loc-regexp (string-match loc-regexp text))
+                (loc-regexp   (realgud-loc-pat-regexp loc-pat))
+                (found-locs nil)
+                (current-pos 0))
+            (while (and loc-regexp current-pos (string-match loc-regexp text current-pos))
               (let* ((bp-nums-str (match-string bp-num-group text))
                      (bp-num-strs (split-string bp-nums-str "[^0-9]+" t))
                      (bp-nums (mapcar #'string-to-number bp-num-strs))
                      (info realgud-cmdbuf-info)
-                     (all-bps (realgud-cmdbuf-info-bp-list info))
-                     (found-locs nil))
+                     (all-bps (realgud-cmdbuf-info-bp-list info)))
                 (dolist (loc all-bps)
                   (when (memq (realgud-loc-num loc) bp-nums)
                     (push loc found-locs)
                     ;; Remove loc from breakpoint list
                     (realgud-cmdbuf-info-bp-list=
                      (remove loc (realgud-cmdbuf-info-bp-list info)))))
-                ;; return the locations
-                found-locs))))))))
+                (setq current-pos (match-end 0))))
+                ;; Match-end returns 0 when the whole string was matched.
+                ;; Setting current-pos to nil exits the loop
+                (if (= current-pos 0) (setq current-pos nil))
+            ;; return the locations
+            found-locs))))))
 
 (defun realgud-track-bp-enable-disable(text loc-pat enable? &optional cmdbuf)
   "Do regular-expression matching see if a breakpoint has been enabled or disabled inside

realgud/debugger/gdb/gdb.el

@@ -145,6 +145,9 @@ fringe and marginal icons.
                 ;; if a relative path is supplied to gcc, gdb will display the relative path
                 ;; tripping up realgud, causing it to ask if you want to blacklist the file.
                 (realgud-command "set filename-display absolute" nil nil nil)
+                ;; gdb doesn't print a confirmation that a breakpoint was deleted successfully by default.
+                ;; This event listener adds a status message for every deleted breakpoint.
+                (realgud-command "python gdb.events.breakpoint_deleted.connect(lambda b: print(f\"Deleted breakpoint {b.number}\"))" nil nil nil)
 		)))
       )
     ))

realgud/debugger/gdb/init.el

@@ -79,10 +79,13 @@ realgud-loc-pat struct")
 ;; response.
 ;; For example:
 ;;   Deleted breakpoint 1
+;;   Deleted breakpoint 1 Deleted breakpoint 1
 ;;   Deleted breakpoints 1 2 3 4
+;; The event listener seems to trigger twice when a breakpoint is deleted using the
+;; clear command. The regexp works around this by allowing one repetition of the match.
 (setf (gethash "brkpt-del" realgud:gdb-pat-hash)
       (make-realgud-loc-pat
-       :regexp "^Deleted breakpoints? \\(\\([0-9]+ *\\)+\\)\n"
+       :regexp "^\\(?:Deleted breakpoints? \\(\\([0-9]+ *\\)+\\) *\\)\\{1,2\\}\n"
        :num 1))
 
 (defconst realgud:gdb-frame-start-regexp