Improve reproducibility of generated loaddefs file.

* lisp/emacs-lisp/autoload.el (autoload-generate-file-autoloads):
Make the return value the modtime of the input file (if no autoloads).
(update-directory-autoloads): In the "no autoloads" section,
use "most recent modtime" rather than "current time".

; http://lists.gnu.org/archive/html/emacs-devel/2015-06/msg00688.html

1 files changed, 144 insertions, 137 deletions

diff --git a/lisp/emacs-lisp/autoload.el b/lisp/emacs-lisp/autoload.el
index a6fefebf3f5..9d1abdddb2b 100644
--- a/lisp/emacs-lisp/autoload.el
+++ b/lisp/emacs-lisp/autoload.el
@@ -522,116 +522,119 @@ If OUTFILE is non-nil and FILE specifies a `generated-autoload-file'
 different from OUTFILE, then OUTBUF is ignored.
 
 Return non-nil if and only if FILE adds no autoloads to OUTFILE
-\(or OUTBUF if OUTFILE is nil)."
-  (catch 'done
-    (let (load-name
-          (print-length nil)
-          (print-level nil)
-          (print-readably t)           ; This does something in Lucid Emacs.
-          (float-output-format nil)
-          (visited (get-file-buffer file))
-          (otherbuf nil)
-          (absfile (expand-file-name file))
-          ;; nil until we found a cookie.
-          output-start)
-      (with-current-buffer (or visited
-                               ;; It is faster to avoid visiting the file.
-                               (autoload-find-file file))
-        ;; Obey the no-update-autoloads file local variable.
-        (unless no-update-autoloads
-          (or noninteractive (message "Generating autoloads for %s..." file))
-          (setq load-name
-                (if (stringp generated-autoload-load-name)
-                    generated-autoload-load-name
-                  (autoload-file-load-name absfile)))
-          ;; FIXME? Comparing file-names for equality with just equal
-          ;; is fragile, eg if one has an automounter prefix and one
-          ;; does not, but both refer to the same physical file.
-          (when (and outfile
-                     (not
-                      (if (memq system-type '(ms-dos windows-nt))
-                          (equal (downcase outfile)
-                                 (downcase (autoload-generated-file)))
-                        (equal outfile (autoload-generated-file)))))
-            (setq otherbuf t))
-          (save-excursion
-            (save-restriction
-              (widen)
-              (when autoload-builtin-package-versions
-                (let ((version (lm-header "version"))
-                      package)
-                  (and version
-                       (setq version (ignore-errors (version-to-list version)))
-                       (setq package (or (lm-header "package")
-                                         (file-name-sans-extension
-                                          (file-name-nondirectory file))))
-                       (setq output-start (autoload--setup-output
-                                           otherbuf outbuf absfile load-name))
-                       (let ((standard-output (marker-buffer output-start))
-                             (print-quoted t))
-                          (princ `(push (purecopy
-                                             ',(cons (intern package) version))
-                                        package--builtin-versions))
-                          (princ "\n")))))
-
-              (goto-char (point-min))
-              (while (not (eobp))
-                (skip-chars-forward " \t\n\f")
-                (cond
-                 ((looking-at (regexp-quote generate-autoload-cookie))
-                  ;; If not done yet, figure out where to insert this text.
-                  (unless output-start
-                    (setq output-start (autoload--setup-output
-                                        otherbuf outbuf absfile load-name)))
-                  (autoload--print-cookie-text output-start load-name file))
-                 ((looking-at ";")
-                  ;; Don't read the comment.
-                  (forward-line 1))
-                 (t
-                  (forward-sexp 1)
-                  (forward-line 1))))))
-
-          (when output-start
-            (let ((secondary-autoloads-file-buf
-                   (if otherbuf (current-buffer))))
-              (with-current-buffer (marker-buffer output-start)
-                (save-excursion
-                  ;; Insert the section-header line which lists the file name
-                  ;; and which functions are in it, etc.
-                  (goto-char output-start)
-                  (let ((relfile (file-relative-name absfile)))
-                    (autoload-insert-section-header
-                     (marker-buffer output-start)
-                     () load-name relfile
-                     (if secondary-autoloads-file-buf
-                         ;; MD5 checksums are much better because they do not
-                         ;; change unless the file changes (so they'll be
-                         ;; equal on two different systems and will change
-                         ;; less often than time-stamps, thus leading to fewer
-                         ;; unneeded changes causing spurious conflicts), but
-                         ;; using time-stamps is a very useful optimization,
-                         ;; so we use time-stamps for the main autoloads file
-                         ;; (loaddefs.el) where we have special ways to
-                         ;; circumvent the "random change problem", and MD5
-                         ;; checksum in secondary autoload files where we do
-                         ;; not need the time-stamp optimization because it is
-                         ;; already provided by the primary autoloads file.
-                         (md5 secondary-autoloads-file-buf
-                              ;; We'd really want to just use
-                              ;; `emacs-internal' instead.
-                              nil nil 'emacs-mule-unix)
-                       (nth 5 (file-attributes relfile))))
-                    (insert ";;; Generated autoloads from " relfile "\n")))
-                (insert generate-autoload-section-trailer))))
-          (or noninteractive
-              (message "Generating autoloads for %s...done" file)))
-        (or visited
-            ;; We created this buffer, so we should kill it.
-            (kill-buffer (current-buffer))))
-      (or (not output-start)
-          ;; If the entries were added to some other buffer, then the file
-          ;; doesn't add entries to OUTFILE.
-          otherbuf))))
+\(or OUTBUF if OUTFILE is nil).  The actual return value is
+FILE's modification time."
+  (let (load-name
+        (print-length nil)
+        (print-level nil)
+        (print-readably t)           ; This does something in Lucid Emacs.
+        (float-output-format nil)
+        (visited (get-file-buffer file))
+        (otherbuf nil)
+        (absfile (expand-file-name file))
+        ;; nil until we found a cookie.
+        output-start)
+    (when
+        (catch 'done
+          (with-current-buffer (or visited
+                                   ;; It is faster to avoid visiting the file.
+                                   (autoload-find-file file))
+            ;; Obey the no-update-autoloads file local variable.
+            (unless no-update-autoloads
+              (or noninteractive (message "Generating autoloads for %s..." file))
+              (setq load-name
+                    (if (stringp generated-autoload-load-name)
+                        generated-autoload-load-name
+                      (autoload-file-load-name absfile)))
+              ;; FIXME? Comparing file-names for equality with just equal
+              ;; is fragile, eg if one has an automounter prefix and one
+              ;; does not, but both refer to the same physical file.
+              (when (and outfile
+                         (not
+                          (if (memq system-type '(ms-dos windows-nt))
+                              (equal (downcase outfile)
+                                     (downcase (autoload-generated-file)))
+                            (equal outfile (autoload-generated-file)))))
+                (setq otherbuf t))
+              (save-excursion
+                (save-restriction
+                  (widen)
+                  (when autoload-builtin-package-versions
+                    (let ((version (lm-header "version"))
+                          package)
+                      (and version
+                           (setq version (ignore-errors (version-to-list version)))
+                           (setq package (or (lm-header "package")
+                                             (file-name-sans-extension
+                                              (file-name-nondirectory file))))
+                           (setq output-start (autoload--setup-output
+                                               otherbuf outbuf absfile load-name))
+                           (let ((standard-output (marker-buffer output-start))
+                                 (print-quoted t))
+                             (princ `(push (purecopy
+                                            ',(cons (intern package) version))
+                                           package--builtin-versions))
+                             (princ "\n")))))
+
+                  (goto-char (point-min))
+                  (while (not (eobp))
+                    (skip-chars-forward " \t\n\f")
+                    (cond
+                     ((looking-at (regexp-quote generate-autoload-cookie))
+                      ;; If not done yet, figure out where to insert this text.
+                      (unless output-start
+                        (setq output-start (autoload--setup-output
+                                            otherbuf outbuf absfile load-name)))
+                      (autoload--print-cookie-text output-start load-name file))
+                     ((looking-at ";")
+                      ;; Don't read the comment.
+                      (forward-line 1))
+                     (t
+                      (forward-sexp 1)
+                      (forward-line 1))))))
+
+              (when output-start
+                (let ((secondary-autoloads-file-buf
+                       (if otherbuf (current-buffer))))
+                  (with-current-buffer (marker-buffer output-start)
+                    (save-excursion
+                      ;; Insert the section-header line which lists the file name
+                      ;; and which functions are in it, etc.
+                      (goto-char output-start)
+                      (let ((relfile (file-relative-name absfile)))
+                        (autoload-insert-section-header
+                         (marker-buffer output-start)
+                         () load-name relfile
+                         (if secondary-autoloads-file-buf
+                             ;; MD5 checksums are much better because they do not
+                             ;; change unless the file changes (so they'll be
+                             ;; equal on two different systems and will change
+                             ;; less often than time-stamps, thus leading to fewer
+                             ;; unneeded changes causing spurious conflicts), but
+                             ;; using time-stamps is a very useful optimization,
+                             ;; so we use time-stamps for the main autoloads file
+                             ;; (loaddefs.el) where we have special ways to
+                             ;; circumvent the "random change problem", and MD5
+                             ;; checksum in secondary autoload files where we do
+                             ;; not need the time-stamp optimization because it is
+                             ;; already provided by the primary autoloads file.
+                             (md5 secondary-autoloads-file-buf
+                                  ;; We'd really want to just use
+                                  ;; `emacs-internal' instead.
+                                  nil nil 'emacs-mule-unix)
+                           (nth 5 (file-attributes relfile))))
+                        (insert ";;; Generated autoloads from " relfile "\n")))
+                    (insert generate-autoload-section-trailer))))
+              (or noninteractive
+                  (message "Generating autoloads for %s...done" file)))
+            (or visited
+                ;; We created this buffer, so we should kill it.
+                (kill-buffer (current-buffer))))
+          (or (not output-start)
+              ;; If the entries were added to some other buffer, then the file
+              ;; doesn't add entries to OUTFILE.
+              otherbuf))
+      (nth 5 (file-attributes absfile)))))
 
 (defun autoload-save-buffers ()
   (while autoload-modified-buffers
@@ -757,7 +760,7 @@ write its autoloads into the specified file instead."
                                                   t files-re))
                                dirs)))
          (done ())
-         (this-time (current-time))
+         (last-time)
          ;; Files with no autoload cookies or whose autoloads go to other
          ;; files because of file-local autoload-generated-file settings.
          (no-autoloads nil)
@@ -782,14 +785,14 @@ write its autoloads into the specified file instead."
                    ;; There shouldn't be more than one such entry.
                    ;; Remove the obsolete section.
                    (autoload-remove-section (match-beginning 0))
-                   (let ((last-time (nth 4 form)))
-                     (dolist (file file)
-                       (let ((file-time (nth 5 (file-attributes file))))
-                         (when (and file-time
-                                    (not (time-less-p last-time file-time)))
-                           ;; file unchanged
-                           (push file no-autoloads)
-                           (setq files (delete file files)))))))
+                   (setq last-time (nth 4 form))
+                   (dolist (file file)
+                     (let ((file-time (nth 5 (file-attributes file))))
+                       (when (and file-time
+                                  (not (time-less-p last-time file-time)))
+                         ;; file unchanged
+                         (push file no-autoloads)
+                         (setq files (delete file files))))))
                   ((not (stringp file)))
                   ((or (not (file-exists-p file))
                        ;; Remove duplicates as well, just in case.
@@ -811,24 +814,28 @@ write its autoloads into the specified file instead."
             (push file done)
             (setq files (delete file files)))))
       ;; Elements remaining in FILES have no existing autoload sections yet.
-      (dolist (file files)
-        (cond
-         ((member (expand-file-name file) autoload-excludes) nil)
-         ;; Passing nil as second argument forces
-         ;; autoload-generate-file-autoloads to look for the right
-         ;; spot where to insert each autoloads section.
-         ((autoload-generate-file-autoloads file nil buffer-file-name)
-          (push file no-autoloads))))
-
-      (when no-autoloads
-        ;; Sort them for better readability.
-        (setq no-autoloads (sort no-autoloads 'string<))
-        ;; Add the `no-autoloads' section.
-        (goto-char (point-max))
-        (search-backward "\f" nil t)
-        (autoload-insert-section-header
-         (current-buffer) nil nil no-autoloads this-time)
-        (insert generate-autoload-section-trailer))
+      (let ((no-autoloads-time (or last-time '(0 0 0 0))) file-time)
+        (dolist (file files)
+          (cond
+           ((member (expand-file-name file) autoload-excludes) nil)
+           ;; Passing nil as second argument forces
+           ;; autoload-generate-file-autoloads to look for the right
+           ;; spot where to insert each autoloads section.
+           ((setq file-time
+                  (autoload-generate-file-autoloads file nil buffer-file-name))
+            (push file no-autoloads)
+            (if (time-less-p no-autoloads-time file-time)
+                (setq no-autoloads-time file-time)))))
+
+        (when no-autoloads
+          ;; Sort them for better readability.
+          (setq no-autoloads (sort no-autoloads 'string<))
+          ;; Add the `no-autoloads' section.
+          (goto-char (point-max))
+          (search-backward "\f" nil t)
+          (autoload-insert-section-header
+           (current-buffer) nil nil no-autoloads no-autoloads-time)
+          (insert generate-autoload-section-trailer)))
 
       (let ((version-control 'never))
         (save-buffer))