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| | ;;; debug-early.el --- Dump a Lisp backtrace without frills -*- lexical-binding: t; -*-
;; Copyright (C) 2022 Free Software Foundation, Inc.
;; Author: Alan Mackenzie <acm@muc.de>
;; Maintainer: emacs-devel@gnu.org
;; Keywords: internal, backtrace, bootstrap.
;; Package: emacs
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; This file dumps a backtrace on stderr when an error is thrown.
;; It has no dependencies on any Lisp libraries and is thus suitable
;; for generating backtraces in the early parts of bootstrapping. It
;; is also good for generating backtraces in batch mode in general.
(defalias 'debug-early-backtrace
#'(lambda ()
"Print a trace of Lisp function calls currently active.
The output stream used is the value of `standard-output'.
This is a simplified version of the standard `backtrace'
function, intended for use in debugging the early parts
of the build process."
(princ "\n")
(mapbacktrace
#'(lambda (evald func args _flags)
(let ((args args))
(if evald
(progn
(princ " ")
(prin1 func)
(princ "(")
(while args
(prin1 (car args))
(setq args (cdr args))
(if args
(princ " ")))
(princ ")\n"))
(while args
(princ " ")
(prin1 (car args))
(princ "\n")
(setq args (cdr args)))))))))
(defalias 'debug-early
#'(lambda (&rest args)
"Print an error message with a backtrace of active Lisp function calls.
The output stream used is the value of `standard-output'.
There should be two ARGS: the symbol `error' (which is ignored)
and a cons of the error symbol and the error data.
This is a simplified version of `debug', intended to produce
diagnostics to help in debugging the early parts of the build
process. It is typically called by the Emacs core when an error
is signaled.
`debug-early' is the default value of the symbol `debugger'
before enough Lisp has been loaded to support `debug' itself, and
in batch mode."
(princ "\nError: ")
(prin1 (car (car (cdr args)))) ; The error symbol.
(princ " ")
(prin1 (cdr (car (cdr args)))) ; The error data.
(debug-early-backtrace)))
;;; debug-early.el ends here.
|