Re: Feature request: A way to get a traceback to a buffer or a string

[Lennart Borgman (gmail)]

Lennart Borgman (gmail) wrote:
> In some situations you may know that a function call will cause an 
> error. You may then want to get a traceback from this particular call, 
> without user intervention. I have attached a macro that can give this. I 
> would find it practical if this were included in Emacs.
>
> (defmacro mumamo-get-backtrace (bodyform)
>   "Evaluate BODYFORM, return backtrace as a string.
> If there is an error in BODYFORM then return the backtrace as a
> string, otherwise return nil."
>   `(let ((debugger (lambda (&rest debugger-args)
>                      (setq debugger-ret (with-output-to-string 
> (backtrace)))))
>          (debug-on-error t)
>          (debug-on-signal t)
>          (debugger-ret nil))
>      (condition-case err
>          (progn
>            ,bodyform
>            nil)
>        (error
>         (let* ((errmsg (error-message-string err))
>                (debugger-lines (split-string debugger-ret "\n"))
>                (dbg-ret (mapconcat 'identity (nthcdr 6 debugger-lines) 
> "\n")))
>           (concat errmsg "\n" dbg-ret))))))


The code above does not give a backtrace always, but I think this will:

(defmacro mumamo-get-backtrace-if-error (bodyform)
  "Evaluate BODYFORM, return a list with error message and backtrace.
If there is an error in BODYFORM then return a list with the
error message and the backtrace as a string. Otherwise return
nil."
  `(let* ((debugger
           (lambda (&rest debugger-args)
             (let ((debugger-ret (with-output-to-string (backtrace))))
               ;; I believe we must put the result in a buffer,
               ;; otherwise `condition-case' might erase it:
               (with-current-buffer (get-buffer-create "TEMP GET 
BACKTRACE")
                 (erase-buffer)
                 (insert debugger-ret)))))
          (debug-on-error t)
          (debug-on-signal t))
     (condition-case err
         (progn
           ,bodyform
           nil)
       (error
        (let* ((errmsg (error-message-string err))
               (dbg1-ret
                (with-current-buffer
                    (get-buffer "TEMP GET BACKTRACE") (buffer-string)))
               ;; Remove lines from this routine:
               (debugger-lines (split-string dbg1-ret "\n"))
               (dbg-ret (mapconcat 'identity (nthcdr 6 debugger-lines) 
"\n"))
               )
          (list errmsg (concat errmsg "\n" dbg-ret)))))))