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guile/module/system/repl/error-handling.scm
Andy Wingo 5273854080 finally, backtraces only showing frames for the computation
* module/system/repl/repl.scm (run-repl): Run the thunk in a stack in a
  prompt, similar to the default prompt. Gives proper backtraces.

* module/system/repl/error-handling.scm (call-with-error-handling):
  Narrow one more outer frame, for the %start-stack thunk invocation.

* module/ice-9/boot-9.scm (%start-stack): Reindent.
2010-07-10 12:21:50 +02:00

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;;; Error handling in the REPL
;; Copyright (C) 2001, 2009, 2010 Free Software Foundation, Inc.
;; This library is free software; you can redistribute it and/or
;; modify it under the terms of the GNU Lesser General Public
;; License as published by the Free Software Foundation; either
;; version 3 of the License, or (at your option) any later version.
;;
;; This library 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
;; Lesser General Public License for more details.
;;
;; You should have received a copy of the GNU Lesser General Public
;; License along with this library; if not, write to the Free Software
;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
;; 02110-1301 USA
;;; Code:
(define-module (system repl error-handling)
#:use-module (system base pmatch)
#:use-module (system repl debug)
#:export (call-with-error-handling
with-error-handling))
;;;
;;; Error handling via repl debugging
;;;
(define* (call-with-error-handling thunk #:key
(on-error 'debug) (post-error 'catch)
(pass-keys '(quit)))
(let ((in (current-input-port))
(out (current-output-port))
(err (current-error-port)))
(define (with-saved-ports thunk)
(with-input-from-port in
(lambda ()
(with-output-to-port out
(lambda ()
(with-error-to-port err
thunk))))))
(catch #t
(lambda () (%start-stack #t thunk))
(case post-error
((catch)
(lambda (key . args)
(if (memq key pass-keys)
(apply throw key args)
(begin
(pmatch args
((,subr ,msg ,args . ,rest)
(with-saved-ports
(lambda ()
(run-hook before-error-hook)
(display-error #f err subr msg args rest)
(run-hook after-error-hook)
(force-output err))))
(else
(format err "\nERROR: uncaught throw to `~a', args: ~a\n"
key args)))
(if #f #f)))))
(else
(if (procedure? post-error)
post-error ; a handler proc
(error "Unknown post-error strategy" post-error))))
(case on-error
((debug)
(lambda (key . args)
(let ((stack (make-stack #t)))
(with-saved-ports
(lambda ()
(pmatch args
((,subr ,msg ,args . ,rest)
(format #t "Throw to key `~a':\n" key)
(display-error stack (current-output-port) subr msg args rest))
(else
(format #t "Throw to key `~a' with args `~s'." key args)))
(format #t "Entering a new prompt. Type `,bt' for a backtrace")
(format #t " or `,q' to return to the old prompt.\n")
(let ((debug
(make-debug
(let ((tag (and (pair? (fluid-ref %stacks))
(cdar (fluid-ref %stacks)))))
(narrow-stack->vector
stack
;; Cut three frames from the top of the stack:
;; make-stack, this one, and the throw handler.
3
;; Narrow the end of the stack to the most recent
;; start-stack.
tag
;; And one more frame, because %start-stack invoking
;; the start-stack thunk has its own frame too.
0 (and tag 1)))
0)))
((@ (system repl repl) start-repl) #:debug debug)))))))
((pass)
(lambda (key . args)
;; fall through to rethrow
#t))
(else
(if (procedure? on-error)
on-error ; pre-unwind handler
(error "Unknown on-error strategy" on-error)))))))
(define-syntax with-error-handling
(syntax-rules ()
((_ form)
(call-with-error-handling (lambda () form)))))