admin/find-gc.el

   1 ;;; find-gc.el --- detect functions that call the garbage collector  -*- lexical-binding: t; -*-
   2
   3 ;; Copyright (C) 1992, 2001-2024 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: emacs-devel@gnu.org
   6
   7 ;; This file is part of GNU Emacs.
   8
   9 ;; GNU Emacs is free software: you can redistribute it and/or modify
  10 ;; it under the terms of the GNU General Public License as published by
  11 ;; the Free Software Foundation, either version 3 of the License, or
  12 ;; (at your option) any later version.
  13
  14 ;; GNU Emacs is distributed in the hope that it will be useful,
  15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;; GNU General Public License for more details.
  18
  19 ;; You should have received a copy of the GNU General Public License
  20 ;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
  21
  22 ;;; Commentary:
  23
  24 ;; Produce in find-gc-unsafe-list the set of all functions that may invoke GC.
  25 ;; This expects the Emacs sources to live in find-gc-source-directory.
  26
  27 ;;; Code:
  28
  29 (defvar find-gc-unsafe-list nil
  30   "The list of unsafe functions is placed here by `find-gc-unsafe'.")
  31
  32 (defvar find-gc-source-directory
  33   (file-name-as-directory (expand-file-name "src" source-directory))
  34   "Directory containing Emacs C sources.")
  35
  36 (defvar find-gc-subrs-callers nil
  37   "Alist of users of subrs, from GC testing.
  38 Each entry has the form (FUNCTION . FUNCTIONS-THAT-CALL-IT).")
  39
  40 (defvar find-gc-subrs-called nil
  41   "Alist of subrs called, in GC testing.
  42 Each entry has the form (FUNCTION . FUNCTIONS-IT-CALLS).")
  43
  44
  45 ;; Functions on this list are safe, even if they appear to be able
  46 ;; to call the target.
  47
  48 (defvar find-gc-noreturn-list '(Fsignal Fthrow wrong_type_argument))
  49
  50 ;; This was originally generated directory-files, but there were
  51 ;; too many files there that were not actually compiled.  The
  52 ;; list below was created for a HP-UX 7.0 system.
  53
  54 (defvar find-gc-source-files
  55   '("dispnew.c" "scroll.c" "xdisp.c" "window.c"
  56     "term.c" "cm.c" "emacs.c" "keyboard.c" "macros.c"
  57     "keymap.c" "sysdep.c" "buffer.c" "filelock.c"
  58     "insdel.c" "marker.c" "minibuf.c" "fileio.c"
  59     "dired.c" "cmds.c" "casefiddle.c"
  60     "indent.c" "search.c" "regex-emacs.c" "undo.c"
  61     "alloc.c" "data.c" "doc.c" "editfns.c"
  62     "callint.c" "eval.c" "fns.c" "print.c" "lread.c"
  63     "syntax.c" "unexcoff.c"
  64     "bytecode.c" "process.c" "callproc.c" "doprnt.c"
  65     "xterm.c" "xfns.c"))
  66
  67
  68 (defun find-gc-unsafe ()
  69   "Return a list of unsafe functions--that is, which can call GC.
  70 Also store it in `find-gc-unsafe-list'."
  71   (trace-call-tree nil)
  72   (trace-use-tree)
  73   (find-unsafe-funcs 'Fgarbage_collect)
  74   (setq find-gc-unsafe-list
  75         (sort find-gc-unsafe-list
  76               (lambda (x y)
  77                 (string-lessp (car x) (car y))))))
  78
  79 ;; This does a depth-first search to find all functions that can
  80 ;; ultimately call the function "target".  The result is an a-list
  81 ;; in find-gc-unsafe-list; the cars are the unsafe functions, and the cdrs
  82 ;; are (one of) the unsafe functions that these functions directly
  83 ;; call.
  84
  85 (defun find-unsafe-funcs (target)
  86   (setq find-gc-unsafe-list (list (list target)))
  87   (trace-unsafe target))
  88
  89 (defun trace-unsafe (func)
  90   (let ((used (assq func find-gc-subrs-callers)))
  91     (or used
  92         (error "No find-gc-subrs-callers for %s" (car find-gc-unsafe-list)))
  93     (while (setq used (cdr used))
  94       (or (assq (car used) find-gc-unsafe-list)
  95           (memq (car used) find-gc-noreturn-list)
  96           (progn
  97             (push (cons (car used) func) find-gc-unsafe-list)
  98             (trace-unsafe (car used)))))))
  99
 100
 101
 102
 103 (defun trace-call-tree (&optional _ignored)
 104   (message "Setting up directories...")
 105   (setq find-gc-subrs-called nil)
 106   (let ((case-fold-search nil)
 107         (default-directory find-gc-source-directory)
 108         (files find-gc-source-files)
 109         name entry rtlfile)
 110     (dolist (file files)
 111       (message "Compiling %s..." file)
 112       (call-process "gcc" nil nil nil "-I" "." "-I" "../lib"
 113                     "-fdump-rtl-expand" "-o" null-device "-c" file)
 114       (setq rtlfile
 115             (file-expand-wildcards (format "%s.*.expand" file) t))
 116       (if (/= 1 (length rtlfile))
 117           (message "Error compiling `%s'?" file)
 118         (with-temp-buffer
 119           (insert-file-contents (setq rtlfile (car rtlfile)))
 120           (delete-file rtlfile)
 121           (while (re-search-forward ";; Function \\|(call_insn " nil t)
 122             (if (= (char-after (- (point) 3)) ?o)
 123                 (progn
 124                   (looking-at "[a-zA-Z0-9_]+")
 125                   (setq name (intern (match-string 0)))
 126                   (message "%s : %s" (car files) name)
 127                   (setq entry (list name)
 128                         find-gc-subrs-called
 129                         (cons entry find-gc-subrs-called)))
 130               (if (looking-at ".*\n?.*\"\\([A-Za-z0-9_]+\\)\"")
 131                   (progn
 132                     (setq name (intern (match-string 1)))
 133                     (or (memq name (cdr entry))
 134                         (setcdr entry (cons name (cdr entry)))))))))))))
 135
 136 (defun trace-use-tree ()
 137   (setq find-gc-subrs-callers
 138         (mapcar #'list (mapcar #'car find-gc-subrs-called)))
 139   (let ((ptr find-gc-subrs-called)
 140         p2 found)
 141     (while ptr
 142       (setq p2 (car ptr))
 143       (while (setq p2 (cdr p2))
 144         (if (setq found (assq (car p2) find-gc-subrs-callers))
 145             (setcdr found (cons (car (car ptr)) (cdr found)))))
 146       (setq ptr (cdr ptr)))))
 147
 148 (provide 'find-gc)
 149
 150 ;;; find-gc.el ends here