Unconditionally reset load-path after dumping

* src/lread.c: (dump_path): Remove.
(load-path-default): Remove `changed' argument.
Do not set dump_path permanently.  Simplify.
(init_lread): Simplify.
(syms_of_lread): Remove dump_path.

* lisp/loadup.el (load-path): Warn if site-load or site-init changes it.
No more need to reset it when bootstrapping.

* doc/lispref/internals.texi (Building Emacs):
* doc/lispref/loading.texi (Library Search): Mention that site-load,
site-init cannot change load-path.

* INSTALL: No longer mention load-path and site-init/site-load.

* etc/NEWS: Mention this.

Fixes: debbugs:16107

10 files changed, 140 insertions, 153 deletions

diff --git a/ChangeLog b/ChangeLog
index d1404a0c01c..c182c165f57 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2013-12-13  Glenn Morris  <rgm@gnu.org>
+
+        * INSTALL: No longer mention load-path and site-init/site-load.
+
 2013-12-12  Glenn Morris  <rgm@gnu.org>
 
         * Makefile.in (install-info): Handle missing info/dir.
diff --git a/INSTALL b/INSTALL
index f5c9d8f44ec..3ce82307aab 100644
--- a/INSTALL
+++ b/INSTALL
@@ -468,10 +468,6 @@ variable gets by default!  Make sure you know what kind of value the
 variable should have.  If you don't pay attention to what you are
 doing, you'll make a mistake.
 
-If you set load-path to a different value in site-init.el or
-site-load.el, Emacs will use *precisely* that value when it starts up
-again.  If you do this, you are on your own!
-
 The `site-*.el' files are nonexistent in the distribution.  You do not
 need to create them if you have nothing to put in them.
 
diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 9bdc35a112c..4f5ff0ecf44 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,9 @@
+2013-12-13  Glenn Morris  <rgm@gnu.org>
+
+        * internals.texi (Building Emacs):
+        * loading.texi (Library Search): Mention that site-load,
+        site-init cannot change load-path.
+
 2013-12-12  Glenn Morris  <rgm@gnu.org>
 
         * elisp.texi: Tweak dircategory.
diff --git a/doc/lispref/internals.texi b/doc/lispref/internals.texi
index 06375c1e18e..8cbf3c4e14c 100644
--- a/doc/lispref/internals.texi
+++ b/doc/lispref/internals.texi
@@ -116,6 +116,11 @@ time.)
 expect in an ordinary unmodified Emacs.  If you feel you must override
 normal features for your site, do it with @file{default.el}, so that
 users can override your changes if they wish.  @xref{Startup Summary}.
+Note that if either @file{site-load.el} or @file{site-init.el} changes
+@code{load-path}, the changes will be lost after dumping.
+@xref{Library Search}.  To make a permanent change to
+@code{load-path}, use the @option{--enable-locallisppath} option
+of @command{configure}.
 
   In a package that can be preloaded, it is sometimes necessary (or
 useful) to delay certain evaluations until Emacs subsequently starts
diff --git a/doc/lispref/loading.texi b/doc/lispref/loading.texi
index 0505b67961d..48866a10687 100644
--- a/doc/lispref/loading.texi
+++ b/doc/lispref/loading.texi
@@ -361,12 +361,10 @@ add one or more directories to @code{load-path}.  For example:
 (push "~/.emacs.d/lisp" load-path)
 @end example
 
-  Dumping Emacs uses a special value of @code{load-path}.  If the
-value of @code{load-path} at the end of dumping is unchanged (that is,
-still the same special value), the dumped Emacs switches to the
-ordinary @code{load-path} value when it starts up, as described above.
-But if @code{load-path} has any other value at the end of dumping,
-that value is used for execution of the dumped Emacs also.
+  Dumping Emacs uses a special value of @code{load-path}.  If you use
+a @file{site-load.el} or @file{site-init.el} file to customize the
+dumped Emacs (@pxref{Building Emacs}), any changes to @code{load-path}
+that these files make will be lost after dumping.
 
 @deffn Command locate-library library &optional nosuffix path interactive-call
 This command finds the precise file name for library @var{library}.  It
diff --git a/etc/NEWS b/etc/NEWS
index 3538eddb968..f4fc27d0562 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -77,6 +77,12 @@ was replaced by ".", so use an explicit "." now if that is what you want.)
 will instead append, if the argument begins with `:' (or `;' on MS Windows;
 i.e., `path-separator').
 
++++
+** If you use either site-load.el or site-init.el to customize the dumped
+Emacs executable, any changes to `load-path' that these files make
+will no longer be present after dumping.  To affect a permanent change
+to `load-path', use the `--enable-locallisppath' option of `configure'.
+
 
 * Changes in Emacs 24.4
 
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 8bd026470d1..8dd26cf294e 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2013-12-13  Glenn Morris  <rgm@gnu.org>
+
+        * loadup.el (load-path): Warn if site-load or site-init changes it.
+        No more need to reset it when bootstrapping.
+
 2013-12-13  Teodor Zlatanov  <tzz@lifelogs.com>
 
         * progmodes/cfengine.el (cfengine-cf-promises): Add more default
diff --git a/lisp/loadup.el b/lisp/loadup.el
index b72ddc0955b..520fe4e701e 100644
--- a/lisp/loadup.el
+++ b/lisp/loadup.el
@@ -46,9 +46,6 @@
 ;; Add subdirectories to the load-path for files that might get
 ;; autoloaded when bootstrapping.
 ;; This is because PATH_DUMPLOADSEARCH is just "../lisp".
-;; Note that we reset load-path below just before dumping,
-;; since lread.c:init_lread checks for changes to load-path
-;; in deciding whether to modify it.
 (if (or (equal (nth 3 command-line-args) "bootstrap")
         (equal (nth 4 command-line-args) "bootstrap")
         ;; FIXME this is irritatingly fragile.
@@ -293,8 +290,15 @@
 ;; you may load them with a "site-load.el" file.
 ;; But you must also cause them to be scanned when the DOC file
 ;; is generated.
-;; For other systems, you must edit ../src/Makefile.in.
-(load "site-load" t)
+(let ((lp load-path))
+  (load "site-load" t)
+  ;; We reset load-path after dumping.
+  ;; For a permanent change in load-path, use configure's
+  ;; --enable-locallisppath option.
+  ;; See http://debbugs.gnu.org/16107 for more details.
+  (or (equal lp load-path)
+      (message "Warning: Change in load-path due to site-load will be \
+lost after dumping")))
 
 ;; Make sure default-directory is unibyte when dumping.  This is
 ;; because we cannot decode and encode it correctly (since the locale
@@ -342,8 +346,13 @@
 
 ;; Note: You can cause additional libraries to be preloaded
 ;; by writing a site-init.el that loads them.
-;; See also "site-load" above.
-(load "site-init" t)
+;; See also "site-load" above
+(let ((lp load-path))
+  (load "site-init" t)
+  (or (equal lp load-path)
+      (message "Warning: Change in load-path due to site-init will be \
+lost after dumping")))
+
 (setq current-load-list nil)
 
 ;; We keep the load-history data in PURE space.
@@ -353,11 +362,6 @@
 
 (set-buffer-modified-p nil)
 
-;; reset the load-path.  See lread.c:init_lread why.
-(if (or (equal (nth 3 command-line-args) "bootstrap")
-        (equal (nth 4 command-line-args) "bootstrap"))
-    (setcdr load-path nil))
-
 (remove-hook 'after-load-functions (lambda (f) (garbage-collect)))
 
 (setq inhibit-load-charset-map nil)
diff --git a/src/ChangeLog b/src/ChangeLog
index 4e8285e9530..0b0ed9452ee 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2013-12-13  Glenn Morris  <rgm@gnu.org>
+
+        * lread.c: Unconditionally reset load-path after dumping.  (Bug#16107)
+        (dump_path): Remove.
+        (load-path-default): Remove `changed' argument.
+        Do not set dump_path permanently.  Simplify.
+        (init_lread): Simplify.
+        (syms_of_lread): Remove dump_path.
+
 2013-12-13  Dmitry Antipov  <dmantipov@yandex.ru>
 
         * alloc.c, font.c, font.h, ftfont.c, ftxfont.c, macfont.m,
diff --git a/src/lread.c b/src/lread.c
index a64f083a5ac..5d02b2bd20b 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -4128,10 +4128,6 @@ load_path_check (Lisp_Object lpath)
     }
 }
 
-/* Record the value of load-path used at the start of dumping
-   so we can see if the site changed it later during dumping.  */
-static Lisp_Object dump_path;
-
 /* Return the default load-path, to be used if EMACSLOADPATH is unset.
    This does not include the standard site-lisp directories
    under the installation prefix (i.e., PATH_SITELOADSEARCH),
@@ -4145,18 +4141,16 @@ static Lisp_Object dump_path;
    If purify-flag (ie dumping) just use PATH_DUMPLOADSEARCH.
    Otherwise use PATH_LOADSEARCH.
 
-   If !initialized, then just set dump_path and return PATH_DUMPLOADSEARCH.
-   If initialized, then if Vload_path != dump_path, return just Vload_path.
-   (Presumably the load-path has already been changed by something.
-   This can only be from a site-load file during dumping.)
+   If !initialized, then just return PATH_DUMPLOADSEARCH.
+   If initialized:
    If Vinstallation_directory is not nil (ie, running uninstalled):
    If installation-dir/lisp exists and not already a member,
    we must be running uninstalled.  Reset the load-path
    to just installation-dir/lisp.  (The default PATH_LOADSEARCH
    refers to the eventual installation directories.  Since we
    are not yet installed, we should not use them, even if they exist.)
-   If installation-dir/lisp does not exist, just add dump_path at the
-   end instead.
+   If installation-dir/lisp does not exist, just add
+   PATH_DUMPLOADSEARCH at the end instead.
    Add installation-dir/site-lisp (if !no_site_lisp, and exists
    and not already a member) at the front.
    If installation-dir != source-dir (ie running an uninstalled,
@@ -4165,7 +4159,7 @@ static Lisp_Object dump_path;
    check), then repeat the above steps for source-dir/lisp, site-lisp.  */
 
 static Lisp_Object
-load_path_default (bool changed)
+load_path_default ()
 {
   Lisp_Object lpath = Qnil;
   const char *normal;
@@ -4186,131 +4180,108 @@ load_path_default (bool changed)
 
   normal = NILP (Vpurify_flag) ? PATH_LOADSEARCH : PATH_DUMPLOADSEARCH;
 
-  /* In a dumped Emacs, we normally reset the value of Vload_path using
-     PATH_LOADSEARCH, since the value that was dumped uses lisp/ in
-     the source directory, instead of the path of the installed elisp
-     libraries.  However, if it appears that Vload_path has already been
-     changed from the default that was saved before dumping, don't
-     change it further.  Changes can only be due to site-lisp
-     files that were processed during dumping.  */
-  /* FIXME?  AFAICS, it does not make sense to change load-path in a
-     dumped site-lisp file, so maybe we should just drop this check.
-     E.g., if you add an element to load-path, you are going to be
-     adding it to PATH_DUMPLOADSEARCH, which refers to the source directory.
-     This will make no sense (and may not still exist) in an installed Emacs.
-     And the only change it is sensible to make to load-path is to add
-     something to the front, which you should do with configure's
-     --enable-locallisppath option if you really want to have it dumped.  */
   if (initialized)
     {
-      if (changed || NILP (Fequal (dump_path, Vload_path)))
-        {
-          /* Do not make any changes.  */
-          return Vload_path;
-        }
-      else
-        {
 #ifdef HAVE_NS
-          const char *loadpath = ns_load_path ();
-          lpath = decode_env_path (0, loadpath ? loadpath : normal, 0);
+      const char *loadpath = ns_load_path ();
+      lpath = decode_env_path (0, loadpath ? loadpath : normal, 0);
 #else
-          lpath = decode_env_path (0, normal, 0);
+      lpath = decode_env_path (0, normal, 0);
 #endif
-          if (!NILP (Vinstallation_directory))
+      if (!NILP (Vinstallation_directory))
+        {
+          Lisp_Object tem, tem1;
+
+          /* Add to the path the lisp subdir of the installation
+             dir, if it is accessible.  Note: in out-of-tree builds,
+             this directory is empty save for Makefile.  */
+          tem = Fexpand_file_name (build_string ("lisp"),
+                                   Vinstallation_directory);
+          tem1 = Ffile_accessible_directory_p (tem);
+          if (!NILP (tem1))
+            {
+              if (NILP (Fmember (tem, lpath)))
+                {
+                  /* We are running uninstalled.  The default load-path
+                     points to the eventual installed lisp directories.
+                     We should not use those now, even if they exist,
+                     so start over from a clean slate.  */
+                  lpath = list1 (tem);
+                }
+            }
+          else
+            /* That dir doesn't exist, so add the build-time
+               Lisp dirs instead.  */
             {
-              Lisp_Object tem, tem1;
+              Lisp_Object dump_path =
+                decode_env_path (0, PATH_DUMPLOADSEARCH, 0);
+              lpath = nconc2 (lpath, dump_path);
+            }
 
-              /* Add to the path the lisp subdir of the installation
-                 dir, if it is accessible.  Note: in out-of-tree builds,
-                 this directory is empty save for Makefile.  */
-              tem = Fexpand_file_name (build_string ("lisp"),
+          /* Add site-lisp under the installation dir, if it exists.  */
+          if (!no_site_lisp)
+            {
+              tem = Fexpand_file_name (build_string ("site-lisp"),
                                        Vinstallation_directory);
               tem1 = Ffile_accessible_directory_p (tem);
               if (!NILP (tem1))
                 {
                   if (NILP (Fmember (tem, lpath)))
-                    {
-                      /* We are running uninstalled.  The default load-path
-                         points to the eventual installed lisp directories.
-                         We should not use those now, even if they exist,
-                         so start over from a clean slate.  */
-                      lpath = list1 (tem);
-                    }
+                    lpath = Fcons (tem, lpath);
                 }
-              else
-                /* That dir doesn't exist, so add the build-time
-                   Lisp dirs instead.  */
-                lpath = nconc2 (lpath, dump_path);
+            }
 
-              /* Add site-lisp under the installation dir, if it exists.  */
-              if (!no_site_lisp)
-                {
-                  tem = Fexpand_file_name (build_string ("site-lisp"),
-                                           Vinstallation_directory);
-                  tem1 = Ffile_accessible_directory_p (tem);
-                  if (!NILP (tem1))
-                    {
-                      if (NILP (Fmember (tem, lpath)))
-                        lpath = Fcons (tem, lpath);
-                    }
-                }
+          /* If Emacs was not built in the source directory,
+             and it is run from where it was built, add to load-path
+             the lisp and site-lisp dirs under that directory.  */
 
-              /* If Emacs was not built in the source directory,
-                 and it is run from where it was built, add to load-path
-                 the lisp and site-lisp dirs under that directory.  */
+          if (NILP (Fequal (Vinstallation_directory, Vsource_directory)))
+            {
+              Lisp_Object tem2;
+
+              tem = Fexpand_file_name (build_string ("src/Makefile"),
+                                       Vinstallation_directory);
+              tem1 = Ffile_exists_p (tem);
 
-              if (NILP (Fequal (Vinstallation_directory, Vsource_directory)))
+              /* Don't be fooled if they moved the entire source tree
+                 AFTER dumping Emacs.  If the build directory is indeed
+                 different from the source dir, src/Makefile.in and
+                 src/Makefile will not be found together.  */
+              tem = Fexpand_file_name (build_string ("src/Makefile.in"),
+                                       Vinstallation_directory);
+              tem2 = Ffile_exists_p (tem);
+              if (!NILP (tem1) && NILP (tem2))
                 {
-                  Lisp_Object tem2;
-
-                  tem = Fexpand_file_name (build_string ("src/Makefile"),
-                                           Vinstallation_directory);
-                  tem1 = Ffile_exists_p (tem);
-
-                  /* Don't be fooled if they moved the entire source tree
-                     AFTER dumping Emacs.  If the build directory is indeed
-                     different from the source dir, src/Makefile.in and
-                     src/Makefile will not be found together.  */
-                  tem = Fexpand_file_name (build_string ("src/Makefile.in"),
-                                           Vinstallation_directory);
-                  tem2 = Ffile_exists_p (tem);
-                  if (!NILP (tem1) && NILP (tem2))
-                    {
-                      tem = Fexpand_file_name (build_string ("lisp"),
-                                               Vsource_directory);
+                  tem = Fexpand_file_name (build_string ("lisp"),
+                                           Vsource_directory);
 
-                      if (NILP (Fmember (tem, lpath)))
-                        lpath = Fcons (tem, lpath);
+                  if (NILP (Fmember (tem, lpath)))
+                    lpath = Fcons (tem, lpath);
 
-                      if (!no_site_lisp)
+                  if (!no_site_lisp)
+                    {
+                      tem = Fexpand_file_name (build_string ("site-lisp"),
+                                               Vsource_directory);
+                      tem1 = Ffile_accessible_directory_p (tem);
+                      if (!NILP (tem1))
                         {
-                          tem = Fexpand_file_name (build_string ("site-lisp"),
-                                                   Vsource_directory);
-                          tem1 = Ffile_accessible_directory_p (tem);
-                          if (!NILP (tem1))
-                            {
-                              if (NILP (Fmember (tem, lpath)))
-                                lpath = Fcons (tem, lpath);
-                            }
+                          if (NILP (Fmember (tem, lpath)))
+                            lpath = Fcons (tem, lpath);
                         }
                     }
-                } /* Vinstallation_directory != Vsource_directory */
-
-            } /* if Vinstallation_directory */
+                }
+            } /* Vinstallation_directory != Vsource_directory */
 
-        } /* if dump_path == Vload_path */
+        } /* if Vinstallation_directory */
     }
   else                          /* !initialized */
     {
       /* NORMAL refers to PATH_DUMPLOADSEARCH, ie the lisp dir in the
          source directory.  We used to add ../lisp (ie the lisp dir in
-         the build directory) at the front here, but that caused trouble
-         because it was copied from dump_path into Vload_path, above,
-         when Vinstallation_directory was non-nil.  It should not be
-         necessary, since in out of tree builds lisp/ is empty, save
+         the build directory) at the front here, but that should not
+         be necessary, since in out of tree builds lisp/ is empty, save
          for Makefile.  */
       lpath = decode_env_path (0, normal, 0);
-      dump_path = lpath;
     }
 #endif /* !CANNOT_DUMP */
 
@@ -4322,27 +4293,20 @@ init_lread (void)
 {
   /* First, set Vload_path.  */
 
-  /* NB: Do not change Vload_path before calling load_path_default,
-     since it may check it against dump_path.
-     (This behavior could be changed.)  */
-
   /* We explicitly ignore EMACSLOADPATH when dumping.  */
   if (NILP (Vpurify_flag) && egetenv ("EMACSLOADPATH"))
     {
-      Lisp_Object elpath = decode_env_path ("EMACSLOADPATH", 0, 1);
+      Vload_path = decode_env_path ("EMACSLOADPATH", 0, 1);
 
       /* Check (non-nil) user-supplied elements.  */
-      load_path_check (elpath);
+      load_path_check (Vload_path);
 
       /* If no nils in the environment variable, use as-is.
          Otherwise, replace any nils with the default.  */
-      if (NILP (Fmemq (Qnil, elpath)))
-        {
-          Vload_path = elpath;
-        }
-      else
+      if (! NILP (Fmemq (Qnil, Vload_path)))
         {
-          Lisp_Object elem, default_lpath = load_path_default (0);
+          Lisp_Object elem, elpath = Vload_path;
+          Lisp_Object default_lpath = load_path_default ();
 
           /* Check defaults, before adding site-lisp.  */
           load_path_check (default_lpath);
@@ -4372,13 +4336,7 @@ init_lread (void)
     }
   else                          /* Vpurify_flag || !EMACSLOADPATH */
     {
-#ifdef CANNOT_DUMP
-      bool changed = 0;
-#else
-      bool changed = initialized && NILP (Fequal (dump_path, Vload_path));
-#endif
-
-      Vload_path = load_path_default (changed);
+      Vload_path = load_path_default ();
 
       /* Check before adding site-lisp directories.
          The install should have created them, but they are not
@@ -4386,10 +4344,8 @@ init_lread (void)
          Or we might be running before installation.  */
       load_path_check (Vload_path);
 
-      /* Add the site-lisp directories at the front, unless the
-         load-path has already been changed.
-         FIXME?  Should we ignore changed here?  */
-      if (initialized && !no_site_lisp && !changed)
+      /* Add the site-lisp directories at the front.  */
+      if (initialized && !no_site_lisp)
         {
           Lisp_Object sitelisp;
           sitelisp = decode_env_path (0, PATH_SITELOADSEARCH, 0);
@@ -4694,8 +4650,6 @@ variables, this must be set in the first line of a file.  */);
   DEFSYM (Qdir_ok, "dir-ok");
   DEFSYM (Qdo_after_load_evaluation, "do-after-load-evaluation");
 
-  staticpro (&dump_path);
-
   staticpro (&read_objects);
   read_objects = Qnil;
   staticpro (&seen_list);