Re: Extend gdb to filter registers

[Yuan Fu <casouri@gmail.com>]

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Thanks for your kind reply, Eli. Here are some more questions:

* If I found a problem in existing code that is unrelated to my new
  feature but is quite trivial to fix (2~3 lines), should I create a
  new branch and send it as an separate patch to bug tracker, or
  include it in my new feature?

* IIUC, I send the patch to the bug tracker and people will review it,
  is that correct?

* If the patch is a fix, should I first create a bug report and reply
  to that report?

I'm still not quite sure how everything works, hope I'm not too
garrulous.

Attached is the patch for the bug fix. Changes are:

1. gdb-mi uses a buffer to store and parse output from gdb process
   and it is cleared after each complete conversation, however
   the cleanup function is not protected against call to `error'
   in handlers who process the output's content and do various things to it.

2. gdb-mi uses `error' for error messages from gdb, I think it should
   use `user-error' instead because the gdb-mi code is running well,
   the error is from gdb and are normal errors like "symbol not
   found in current context". We shouldn't drop a user into a backtrace
   for errors like this
   
Yuan


[-- Attachment #2: unwind-protect.patch --]
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From 1bbfaa19081c34167722b0806550696f219e261b Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Sat, 5 Oct 2019 23:29:17 -0400
Subject: [PATCH 1/2] Add unwind-protect to error handling function

lisp/progmodes/gdb-mi.el (gdb-done-or-error): add unwind-protect
---
 lisp/progmodes/gdb-mi.el | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/lisp/progmodes/gdb-mi.el b/lisp/progmodes/gdb-mi.el
index 60852e4ad6..042c49c737 100644
--- a/lisp/progmodes/gdb-mi.el
+++ b/lisp/progmodes/gdb-mi.el
@@ -2644,13 +2644,13 @@ gdb-done-or-error
     ;; We are done concatenating to the output sink.  Restore it to user sink:
     (setq gdb-output-sink 'user)
 
-    (when (and token-number is-complete)
-      (with-current-buffer
-	  (gdb-get-buffer-create 'gdb-partial-output-buffer)
-	(gdb-handle-reply (string-to-number token-number))))
-
-  (when is-complete
-    (gdb-clear-partial-output))))
+    (unwind-protect (when (and token-number is-complete)
+                      (with-current-buffer
+	                  (gdb-get-buffer-create 'gdb-partial-output-buffer)
+	                (gdb-handle-reply (string-to-number token-number))))
+      ;; protect against handler-emitted errors
+      (when is-complete
+        (gdb-clear-partial-output)))))
 
 (defun gdb-concat-output (so-far new)
   (cond
-- 
2.23.0


From d76fdd533594153e144f78d47cdb6c2968041a99 Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Sat, 5 Oct 2019 23:39:05 -0400
Subject: [PATCH 2/2] Change error to user-error

lisp/progmodes/gdb-mi.el
  (gdb-read-memory-custom): Change error to user-error
---
 lisp/progmodes/gdb-mi.el | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lisp/progmodes/gdb-mi.el b/lisp/progmodes/gdb-mi.el
index 042c49c737..1bc451df8e 100644
--- a/lisp/progmodes/gdb-mi.el
+++ b/lisp/progmodes/gdb-mi.el
@@ -3500,7 +3500,8 @@ gdb-read-memory-custom
       (progn
         (let ((gdb-memory-address gdb-memory-last-address))
           (gdb-invalidate-memory 'update)
-          (error err-msg))))))
+          ;; an error from gdb should be considered a user error
+          (user-error err-msg))))))
 
 (defvar gdb-memory-mode-map
   (let ((map (make-sparse-keymap)))
-- 
2.23.0