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;;; disass.el --- disassembler for compiled Emacs Lisp code -*- lexical-binding:t -*-
;; Copyright (C) 1986, 1991, 2002-2018 Free Software Foundation, Inc.
;; Author: Doug Cutting <doug@csli.stanford.edu>
;; Jamie Zawinski <jwz@lucid.com>
;; Maintainer: emacs-devel@gnu.org
;; Keywords: internal
;; 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:
;; The single entry point, `disassemble', disassembles a code object generated
;; by the Emacs Lisp byte-compiler. This doesn't invert the compilation
;; operation, not by a long shot, but it's useful for debugging.
;;
;; Original version by Doug Cutting (doug@csli.stanford.edu)
;; Substantially modified by Jamie Zawinski <jwz@lucid.com> for
;; the new lapcode-based byte compiler.
;;; Code:
(require 'macroexp)
;; The variable byte-code-vector is defined by the new bytecomp.el.
;; The function byte-decompile-lapcode is defined in byte-opt.el.
;; Since we don't use byte-decompile-lapcode, let's try not loading byte-opt.
(require 'byte-compile "bytecomp")
(defvar disassemble-column-1-indent 8 "*")
(defvar disassemble-column-2-indent 10 "*")
(defvar disassemble-recursive-indent 3 "*")
;;;###autoload
(defun disassemble (object &optional buffer indent interactive-p)
"Print disassembled code for OBJECT in (optional) BUFFER.
OBJECT can be a symbol defined as a function, or a function itself
\(a lambda expression or a compiled-function object).
If OBJECT is not already compiled, we compile it, but do not
redefine OBJECT if it is a symbol."
(interactive
(let* ((fn (function-called-at-point))
(prompt (if fn (format "Disassemble function (default %s): " fn)
"Disassemble function: "))
(def (and fn (symbol-name fn))))
(list (intern (completing-read prompt obarray 'fboundp t nil nil def))
nil 0 t)))
(if (and (consp object) (not (functionp object)))
(setq object `(lambda () ,object)))
(or indent (setq indent 0)) ;Default indent to zero
(save-excursion
(if (or interactive-p (null buffer))
(with-output-to-temp-buffer "*Disassemble*"
(set-buffer "*Disassemble*")
(disassemble-internal object indent (not interactive-p)))
(set-buffer buffer)
(disassemble-internal object indent nil)))
nil)
(defun disassemble-internal (obj indent interactive-p)
(let ((macro 'nil)
(name (when (symbolp obj)
(prog1 obj
(setq obj (indirect-function obj)))))
args)
(setq obj (autoload-do-load obj name))
(if (subrp obj)
(error "Can't disassemble #<subr %s>" name))
(if (eq (car-safe obj) 'macro) ;Handle macros.
(setq macro t
obj (cdr obj)))
(if (eq (car-safe obj) 'byte-code)
(setq obj `(lambda () ,obj)))
(when (consp obj)
(unless (functionp obj) (error "not a function"))
(if (assq 'byte-code obj)
nil
(if interactive-p (message (if name
"Compiling %s's definition..."
"Compiling definition...")
name))
(setq obj (byte-compile obj))
(if interactive-p (message "Done compiling. Disassembling..."))))
(cond ((consp obj)
(setq args (help-function-arglist obj)) ;save arg list
(setq obj (cdr obj)) ;throw lambda away
(setq obj (cdr obj)))
((byte-code-function-p obj)
(setq args (help-function-arglist obj)))
(t (error "Compilation failed")))
(if (zerop indent) ; not a nested function
(progn
(indent-to indent)
(insert (format "byte code%s%s%s:\n"
(if (or macro name) " for" "")
(if macro " macro" "")
(if name (format " %s" name) "")))))
(let ((doc (if (consp obj)
(and (stringp (car obj)) (car obj))
;; Use documentation to get lazy-loaded doc string
(documentation obj t))))
(if (and doc (stringp doc))
(progn (and (consp obj) (setq obj (cdr obj)))
(indent-to indent)
(princ " doc: " (current-buffer))
(if (string-match "\n" doc)
(setq doc (concat (substring doc 0 (match-beginning 0))
" ...")))
(insert doc "\n"))))
(indent-to indent)
(insert " args: ")
(prin1 args (current-buffer))
(insert "\n")
(let ((interactive (interactive-form obj)))
(if interactive
(progn
(setq interactive (nth 1 interactive))
(if (eq (car-safe (car-safe obj)) 'interactive)
(setq obj (cdr obj)))
(indent-to indent)
(insert " interactive: ")
(if (eq (car-safe interactive) 'byte-code)
(progn
(insert "\n")
(disassemble-1 interactive
(+ indent disassemble-recursive-indent)))
(let ((print-escape-newlines t))
(prin1 interactive (current-buffer))))
(insert "\n"))))
(cond ((and (consp obj) (assq 'byte-code obj))
(disassemble-1 (assq 'byte-code obj) indent))
((byte-code-function-p obj)
(disassemble-1 obj indent))
(t
(insert "Uncompiled body: ")
(let ((print-escape-newlines t))
(prin1 (macroexp-progn obj)
(current-buffer))))))
(if interactive-p
(message "")))
(defun disassemble-1 (obj indent)
"Prints the byte-code call OBJ in the current buffer.
OBJ should be a call to BYTE-CODE generated by the byte compiler."
(let (bytes constvec)
(if (consp obj)
(setq bytes (car (cdr obj)) ;the byte code
constvec (car (cdr (cdr obj)))) ;constant vector
;; If it is lazy-loaded, load it now
(fetch-bytecode obj)
(setq bytes (aref obj 1)
constvec (aref obj 2)))
(let ((lap (byte-decompile-bytecode (string-as-unibyte bytes) constvec))
op arg opname pc-value)
(let ((tagno 0)
tmp
(lap lap))
(while (setq tmp (assq 'TAG lap))
(setcar (cdr tmp) (setq tagno (1+ tagno)))
(setq lap (cdr (memq tmp lap)))))
(while lap
;; Take off the pc value of the next thing
;; and put it in pc-value.
(setq pc-value nil)
(if (numberp (car lap))
(setq pc-value (car lap)
lap (cdr lap)))
;; Fetch the next op and its arg.
(setq op (car (car lap))
arg (cdr (car lap)))
(setq lap (cdr lap))
(indent-to indent)
(if (eq 'TAG op)
(progn
;; We have a label. Display it, but first its pc value.
(if pc-value
(insert (format "%d:" pc-value)))
(insert (int-to-string (car arg))))
;; We have an instruction. Display its pc value first.
(if pc-value
(insert (format "%d" pc-value)))
(indent-to (+ indent disassemble-column-1-indent))
(if (and op
(string-match "^byte-" (setq opname (symbol-name op))))
(setq opname (substring opname 5))
(setq opname "<not-an-opcode>"))
(if (eq op 'byte-constant2)
(insert " #### shouldn't have seen constant2 here!\n "))
(insert opname)
(indent-to (+ indent disassemble-column-1-indent
disassemble-column-2-indent
-1))
(insert " ")
(cond ((memq op byte-goto-ops)
(insert (int-to-string (nth 1 arg))))
((memq op '(byte-call byte-unbind
byte-listN byte-concatN byte-insertN
byte-stack-ref byte-stack-set byte-stack-set2
byte-discardN byte-discardN-preserve-tos))
(insert (int-to-string arg)))
((memq op '(byte-varref byte-varset byte-varbind))
(prin1 (car arg) (current-buffer)))
((memq op '(byte-constant byte-constant2))
;; it's a constant
(setq arg (car arg))
;; if the succeeding op is byte-switch, display the jump table
;; used
(cond ((eq (car-safe (car-safe (cdr lap))) 'byte-switch)
(insert (format "<jump-table-%s (" (hash-table-test arg)))
(let ((first-time t))
(maphash #'(lambda (value tag)
(if first-time
(setq first-time nil)
(insert " "))
(insert (format "%s %s" value (cadr tag))))
arg))
(insert ")>"))
;; if the value of the constant is compiled code, then
;; recursively disassemble it.
((or (byte-code-function-p arg)
(and (consp arg) (functionp arg)
(assq 'byte-code arg))
(and (eq (car-safe arg) 'macro)
(or (byte-code-function-p (cdr arg))
(and (consp (cdr arg))
(functionp (cdr arg))
(assq 'byte-code (cdr arg))))))
(cond ((byte-code-function-p arg)
(insert "<compiled-function>\n"))
((functionp arg)
(insert "<compiled lambda>"))
(t (insert "<compiled macro>\n")))
(disassemble-internal
arg
(+ indent disassemble-recursive-indent 1)
nil))
((eq (car-safe arg) 'byte-code)
(insert "<byte code>\n")
(disassemble-1 ;recurse on byte-code object
arg
(+ indent disassemble-recursive-indent)))
((eq (car-safe (car-safe arg)) 'byte-code)
(insert "(<byte code>...)\n")
(mapc ;recurse on list of byte-code objects
(lambda (obj)
(disassemble-1
obj
(+ indent disassemble-recursive-indent)))
arg))
(t
;; really just a constant
(let ((print-escape-newlines t))
(prin1 arg (current-buffer))))))
)
(insert "\n")))))
nil)
(provide 'disass)
;;; disass.el ends here
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