Get rid of the AUTOGEN_VCS variable in lisp/Makefile

* lisp/emacs-lisp/autoload.el (autoload-ensure-writable): New variable.
(autoload-ensure-default-file): Maybe make existing output writable.

* lisp/Makefile.in (AUTOGEN_VCS): Remove.
(autoloads): Use autoload-ensure-writable rather than AUTOGEN_VCS.

1 files changed, 19 insertions, 2 deletions

diff --git a/lisp/emacs-lisp/autoload.el b/lisp/emacs-lisp/autoload.el
index 361e8fa7c68..38956df66de 100644
--- a/lisp/emacs-lisp/autoload.el
+++ b/lisp/emacs-lisp/autoload.el
@@ -351,9 +351,26 @@ not be relied upon."
 	    ";;; " basename
 	    " ends here\n")))
 
+(defvar autoload-ensure-writable nil
+  "Non-nil means `autoload-ensure-default-file' makes existing file writable.")
+;; Just in case someone tries to get you to overwrite a file that you
+;; don't want to.
+;;;###autoload
+(put 'autoload-ensure-writable 'risky-local-variable t)
+
 (defun autoload-ensure-default-file (file)
-  "Make sure that the autoload file FILE exists and if not create it."
-  (unless (file-exists-p file)
+  "Make sure that the autoload file FILE exists, creating it if needed.
+If the file already exists and `autoload-ensure-writable' is non-nil,
+make it writable."
+  (if (file-exists-p file)
+      ;; Probably pointless, but replaces the old AUTOGEN_VCS in lisp/Makefile,
+      ;; which was designed to handle CVSREAD=1 and equivalent.
+      (and autoload-ensure-writable
+	   (let ((modes (file-modes file)))
+	     (if (zerop (logand modes #o0200))
+		 ;; Ignore any errors here, and let subsequent attempts
+		 ;; to write the file raise any real error.
+		 (ignore-errors (set-file-modes file (logior modes #o0200))))))
     (write-region (autoload-rubric file) nil file))
   file)