Empty elements in EMACSLOADPATH now stand for the default

* src/lread.c (load_path_check): Take path to check as argument.
(load_path_default): New, split from init_lread.
(init_lread): Move calc of default load-path to load_path_default.
Empty elements in EMACSLOADPATH now stand for the default.
(load-path): Doc fix.

* src/emacs.c (decode_env_path): Add option to treat empty elements
as nil rather than ".".

* src/callproc.c (init_callproc_1, init_callproc):
* src/image.c (Vx_bitmap_file_path):
* src/lisp.h (decode_env_path):
* lread.c (Vsource_directory):
Update for new argument spec of decode_env_path.

* leim/Makefile.in (RUN_EMACS): Empty EMACSLOADPATH rather than unsetting.

* lisp/Makefile.in (emacs): Empty EMACSLOADPATH rather than unsetting.

* test/automated/Makefile.in (emacs):
Empty EMACSLOADPATH rather than unsetting.

* doc/emacs/cmdargs.texi (General Variables):
Empty elements in EMACSLOADPATH now mean the default load-path.

* doc/lispref/loading.texi (Library Search):
Empty elements in EMACSLOADPATH now mean the default load-path.

* etc/NEWS: Mention this.

Fixes: debbugs:12100

17 files changed, 253 insertions, 156 deletions

diff --git a/doc/emacs/ChangeLog b/doc/emacs/ChangeLog
index 229929d132d..a0d5344641e 100644
--- a/doc/emacs/ChangeLog
+++ b/doc/emacs/ChangeLog
@@ -1,3 +1,8 @@
+2013-11-23  Glenn Morris  <rgm@gnu.org>
+
+	* cmdargs.texi (General Variables):
+	Empty elements in EMACSLOADPATH now mean the default load-path.
+
 2013-11-21  Glenn Morris  <rgm@gnu.org>
 
 	* cmdargs.texi (Action Arguments): Use path-separator with -L.
diff --git a/doc/emacs/cmdargs.texi b/doc/emacs/cmdargs.texi
index 92861c443f1..4294f775e5e 100644
--- a/doc/emacs/cmdargs.texi
+++ b/doc/emacs/cmdargs.texi
@@ -455,13 +455,16 @@ This is used to initialize the variable @code{data-directory}.
 Directory for the documentation string file, which is used to
 initialize the Lisp variable @code{doc-directory}.
 @item EMACSLOADPATH
-A colon-separated list of directories@footnote{ Here and below,
+A colon-separated list of directories@footnote{Here and below,
 whenever we say ``colon-separated list of directories'', it pertains
 to Unix and GNU/Linux systems.  On MS-DOS and MS-Windows, the
 directories are separated by semi-colons instead, since DOS/Windows
-file names might include a colon after a drive letter.}  to search for
-Emacs Lisp files.  If set, it overrides the usual initial value of the
-@code{load-path} variable (@pxref{Lisp Libraries}).
+file names might include a colon after a drive letter.} to search for
+Emacs Lisp files.  If set, it modifies the usual initial value of the
+@code{load-path} variable (@pxref{Lisp Libraries}).  An empty element
+stands for the default value of @code{load-path}; e.g., using
+@samp{EMACSLOADPATH="/tmp:"} adds @file{/tmp} to the front of
+the default @code{load-path}.
 @item EMACSPATH
 A colon-separated list of directories to search for executable files.
 If set, Emacs uses this in addition to @env{PATH} (see below) when
diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 8a082a851c9..5251efec3e4 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,8 @@
+2013-11-23  Glenn Morris  <rgm@gnu.org>
+
+	* loading.texi (Library Search):
+	Empty elements in EMACSLOADPATH now mean the default load-path.
+
 2013-11-22  Glenn Morris  <rgm@gnu.org>
 
 	* loading.texi (Library Search): Minor clarification.
diff --git a/doc/lispref/loading.texi b/doc/lispref/loading.texi
index 38a73b4e296..aae92de99cb 100644
--- a/doc/lispref/loading.texi
+++ b/doc/lispref/loading.texi
@@ -310,25 +310,34 @@ directories, if they exist.  Normally these directories do not contain
 @file{site-lisp} directories.)
 
 @cindex @env{EMACSLOADPATH} environment variable
-If the environment variable @env{EMACSLOADPATH} is set, it overrides
-the above initialization procedure.  That is, Emacs initializes
-@code{load-path} based solely on the value of the environment
-variable.  You must therefore include the directory containing the
-standard Lisp files, else Emacs will not function.  In most
-situations, it is better to use the @option{-L} command-line option
-(see below) to add elements to @code{load-path}.
+If the environment variable @env{EMACSLOADPATH} is set, it modifies
+the above initialization procedure.  Emacs initializes
+@code{load-path} based on the value of the environment variable.
 
 The syntax of @env{EMACSLOADPATH} is the same as used for @code{PATH};
 directory names are separated by @samp{:} (or @samp{;}, on some
-operating systems), and @samp{.} stands for the current default
-directory.  Here is an example of how to set @env{EMACSLOADPATH}
-variable (from a @command{sh}-style shell):
+operating systems).
+@ignore
+@c AFAICS, does not (yet) work right to specify non-absolute elements.
+and @samp{.} stands for the current default directory.
+@end ignore
+Here is an example of how to set @env{EMACSLOADPATH} variable (from a
+@command{sh}-style shell):
 
 @example
-export EMACSLOADPATH
-EMACSLOADPATH=/home/foo/.emacs.d/lisp:/usr/local/emacs/24.3/lisp
+export EMACSLOADPATH=/home/foo/.emacs.d/lisp:
 @end example
 
+An empty element in the value of the environment variable, whether
+trailing (as in the above example), leading, or embedded, is replaced
+by the default value of @code{load-path} as determined by the standard
+initialization procedure.  If there are no such empty elements, then
+@env{EMACSLOADPATH} specifies the entire @code{load-path}.  You must
+include either an empty element, or the explicit path to the directory
+containing the standard Lisp files, else Emacs will not function.
+(Another way to modify @code{load-path} is to use the @option{-L}
+command-line option when starting Emacs; see below.)
+
   For each directory in @code{load-path}, Emacs then checks to see if
 it contains a file @file{subdirs.el}, and if so, loads it.  The
 @file{subdirs.el} file is created when Emacs is built/installed,
diff --git a/etc/NEWS b/etc/NEWS
index 97ae6c79d20..4dc1543d845 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -63,6 +63,16 @@ To use the old backend by default, do on the command line:
 * Startup Changes in Emacs 24.4
 
 +++
+** When initializing `load-path', an empty element in the EMACSLOADPATH
+environment variable (either leading, e.g., ":/foo"; trailing, e.g.,
+"/foo:"; or embedded, e.g., "/foo::/bar") is replaced with the default
+load-path (the one that would have been used if EMACSLOADPATH was unset).
+This makes it easier to _extend_ the load-path via EMACSLOADPATH
+(previously, EMACSLOADPATH had to specify the complete load-path,
+including the defaults).  (In older versions of Emacs, an empty element
+was replaced by ".", so use an explicit "." now if that is what you want.)
+
++++
 ** The -L option, which normally prepends its argument to load-path,
 will instead append, if the argument begins with `:' (or `;' on MS Windows;
 i.e., `path-separator').
diff --git a/leim/ChangeLog b/leim/ChangeLog
index 6b16d71c215..ec5d9958151 100644
--- a/leim/ChangeLog
+++ b/leim/ChangeLog
@@ -1,3 +1,7 @@
+2013-11-23  Glenn Morris  <rgm@gnu.org>
+
+	* Makefile.in (RUN_EMACS): Empty EMACSLOADPATH rather than unsetting.
+
 2013-11-04  Eli Zaretskii  <eliz@gnu.org>
 
 	* Makefile.in (RUN_EMACS): Don't set LC_ALL=C.  (Bug#15260)
diff --git a/leim/Makefile.in b/leim/Makefile.in
index a5c05d567ec..5a6f2ff4795 100644
--- a/leim/Makefile.in
+++ b/leim/Makefile.in
@@ -32,8 +32,7 @@ EMACS = ../src/emacs
 
 # How to run Emacs.
 # Prevent any setting of EMACSLOADPATH in user environment causing problems.
-RUN_EMACS = unset EMACSLOADPATH; "${EMACS}" -batch \
-	--no-site-file --no-site-lisp
+RUN_EMACS = EMACSLOADPATH= "${EMACS}" -batch --no-site-file --no-site-lisp
 
 MKDIR_P = @MKDIR_P@
 
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index f9b6f6ee356..97f4c007c72 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,7 @@
+2013-11-23  Glenn Morris  <rgm@gnu.org>
+
+	* Makefile.in (emacs): Empty EMACSLOADPATH rather than unsetting.
+
 2013-11-22  Leo Liu  <sdl.web@gmail.com>
 
 	* progmodes/octave.el (inferior-octave-startup): Spit out error
diff --git a/lisp/Makefile.in b/lisp/Makefile.in
index d00330c3a9b..eb52b317e7b 100644
--- a/lisp/Makefile.in
+++ b/lisp/Makefile.in
@@ -106,7 +106,7 @@ COMPILE_FIRST = \
 
 # The actual Emacs command run in the targets below.
 # Prevent any setting of EMACSLOADPATH in user environment causing problems.
-emacs = unset EMACSLOADPATH; "$(EMACS)" $(EMACSOPT)
+emacs = EMACSLOADPATH= "$(EMACS)" $(EMACSOPT)
 
 # Common command to find subdirectories
 setwins=for file in `find . -type d -print`; do \
diff --git a/src/ChangeLog b/src/ChangeLog
index 994ea2d3de5..823a70326bb 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,19 @@
+2013-11-23  Glenn Morris  <rgm@gnu.org>
+
+	Empty elements in EMACSLOADPATH stand for the default.  (Bug#12100)
+	* lread.c (load_path_check): Take path to check as argument.
+	(load_path_default): New, split from init_lread.
+	(init_lread): Move calc of default load-path to load_path_default.
+	Empty elements in EMACSLOADPATH now stand for the default.
+	(load-path): Doc fix.
+	* emacs.c (decode_env_path): Add option to treat empty elements
+	as nil rather than ".".
+	* callproc.c (init_callproc_1, init_callproc):
+	* image.c (Vx_bitmap_file_path):
+	* lisp.h (decode_env_path):
+	* lread.c (Vsource_directory):
+	Update for new argument spec of decode_env_path.
+
 2013-11-22  Eli Zaretskii  <eliz@gnu.org>
 
 	* bidi.c (bidi_find_paragraph_start): Limit the returned positions
diff --git a/src/callproc.c b/src/callproc.c
index 3317c1203bc..dfe315ab8db 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -1,6 +1,6 @@
 /* Synchronous subprocess invocation for GNU Emacs.
-   Copyright (C) 1985-1988, 1993-1995, 1999-2013
-		 Free Software Foundation, Inc.
+
+Copyright (C) 1985-1988, 1993-1995, 1999-2013 Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
 
@@ -1520,14 +1520,14 @@ init_callproc_1 (void)
 #ifdef HAVE_NS
                                              etc_dir ? etc_dir :
 #endif
-                                             PATH_DATA);
+                                             PATH_DATA, 0);
   Vdata_directory = Ffile_name_as_directory (Fcar (Vdata_directory));
 
   Vdoc_directory = decode_env_path ("EMACSDOC",
 #ifdef HAVE_NS
                                              etc_dir ? etc_dir :
 #endif
-                                             PATH_DOC);
+                                             PATH_DOC, 0);
   Vdoc_directory = Ffile_name_as_directory (Fcar (Vdoc_directory));
 
   /* Check the EMACSPATH environment variable, defaulting to the
@@ -1536,10 +1536,10 @@ init_callproc_1 (void)
 #ifdef HAVE_NS
                                 path_exec ? path_exec :
 #endif
-                                PATH_EXEC);
+                                PATH_EXEC, 0);
   Vexec_directory = Ffile_name_as_directory (Fcar (Vexec_path));
   /* FIXME?  For ns, path_exec should go at the front?  */
-  Vexec_path = nconc2 (decode_env_path ("PATH", ""), Vexec_path);
+  Vexec_path = nconc2 (decode_env_path ("PATH", "", 0), Vexec_path);
 }
 
 /* This is run after init_cmdargs, when Vinstallation_directory is valid.  */
@@ -1580,9 +1580,9 @@ init_callproc (void)
 #ifdef HAVE_NS
 					path_exec ? path_exec :
 #endif
-					PATH_EXEC);
+					PATH_EXEC, 0);
 	  Vexec_path = Fcons (tem, Vexec_path);
-	  Vexec_path = nconc2 (decode_env_path ("PATH", ""), Vexec_path);
+	  Vexec_path = nconc2 (decode_env_path ("PATH", "", 0), Vexec_path);
 	}
 
       Vexec_directory = Ffile_name_as_directory (tem);
diff --git a/src/emacs.c b/src/emacs.c
index 52d2e76dc87..75082ecef7d 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -2167,10 +2167,13 @@ synchronize_system_messages_locale (void)
 
 
 Lisp_Object
-decode_env_path (const char *evarname, const char *defalt)
+decode_env_path (const char *evarname, const char *defalt, bool empty)
 {
   const char *path, *p;
   Lisp_Object lpath, element, tem;
+  /* Default is to use "." for empty path elements.
+     But if argument EMPTY is true, use nil instead.  */
+  Lisp_Object empty_element = empty ? Qnil : build_string (".");
 #ifdef WINDOWSNT
   bool defaulted = 0;
   const char *emacs_dir = egetenv ("emacs_dir");
@@ -2209,34 +2212,38 @@ decode_env_path (const char *evarname, const char *defalt)
       if (!p)
 	p = path + strlen (path);
       element = (p - path ? make_unibyte_string (path, p - path)
-		 : build_string ("."));
+		 : empty_element);
+      if (! NILP (element))
+        {
 #ifdef WINDOWSNT
-      /* Relative file names in the default path are interpreted as
-	 being relative to $emacs_dir.  */
-      if (emacs_dir && defaulted
-	  && strncmp (path, emacs_dir_env, emacs_dir_len) == 0)
-	element = Fexpand_file_name (Fsubstring (element,
-						 make_number (emacs_dir_len),
-						 Qnil),
-				     build_unibyte_string (emacs_dir));
-#endif
-
-      /* Add /: to the front of the name
-	 if it would otherwise be treated as magic.  */
-      tem = Ffind_file_name_handler (element, Qt);
-
-      /* However, if the handler says "I'm safe",
-	 don't bother adding /:.  */
-      if (SYMBOLP (tem))
-	{
-	  Lisp_Object prop;
-	  prop = Fget (tem, intern ("safe-magic"));
-	  if (! NILP (prop))
-	    tem = Qnil;
-	}
+          /* Relative file names in the default path are interpreted as
+             being relative to $emacs_dir.  */
+          if (emacs_dir && defaulted
+              && strncmp (path, emacs_dir_env, emacs_dir_len) == 0)
+            element = Fexpand_file_name (Fsubstring
+                                         (element,
+                                          make_number (emacs_dir_len),
+                                          Qnil),
+                                         build_unibyte_string (emacs_dir));
+#endif
+
+          /* Add /: to the front of the name
+             if it would otherwise be treated as magic.  */
+          tem = Ffind_file_name_handler (element, Qt);
+
+          /* However, if the handler says "I'm safe",
+             don't bother adding /:.  */
+          if (SYMBOLP (tem))
+            {
+              Lisp_Object prop;
+              prop = Fget (tem, intern ("safe-magic"));
+              if (! NILP (prop))
+                tem = Qnil;
+            }
 
-      if (! NILP (tem))
-	element = concat2 (build_string ("/:"), element);
+          if (! NILP (tem))
+            element = concat2 (build_string ("/:"), element);
+        } /* !NILP (element) */
 
       lpath = Fcons (element, lpath);
       if (*p)
diff --git a/src/image.c b/src/image.c
index 37a19e4f5a5..167ee2da303 100644
--- a/src/image.c
+++ b/src/image.c
@@ -9502,7 +9502,7 @@ A cross is always drawn on black & white displays.  */);
 
   DEFVAR_LISP ("x-bitmap-file-path", Vx_bitmap_file_path,
     doc: /* List of directories to search for window system bitmap files.  */);
-  Vx_bitmap_file_path = decode_env_path (0, PATH_BITMAPS);
+  Vx_bitmap_file_path = decode_env_path (0, PATH_BITMAPS, 0);
 
   DEFVAR_LISP ("image-cache-eviction-delay", Vimage_cache_eviction_delay,
     doc: /* Maximum time after which images are removed from the cache.
diff --git a/src/lisp.h b/src/lisp.h
index a9aac2cc0bb..376235a402d 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -1,7 +1,6 @@
 /* Fundamental definitions for GNU Emacs Lisp interpreter.
 
-Copyright (C) 1985-1987, 1993-1995, 1997-2013 Free Software Foundation,
-Inc.
+Copyright (C) 1985-1987, 1993-1995, 1997-2013 Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
 
@@ -4058,7 +4057,7 @@ extern int initial_argc;
 #if defined (HAVE_X_WINDOWS) || defined (HAVE_NS)
 extern bool display_arg;
 #endif
-extern Lisp_Object decode_env_path (const char *, const char *);
+extern Lisp_Object decode_env_path (const char *, const char *, bool);
 extern Lisp_Object empty_unibyte_string, empty_multibyte_string;
 extern Lisp_Object Qfile_name_handler_alist;
 extern _Noreturn void terminate_due_to_signal (int, int);
diff --git a/src/lread.c b/src/lread.c
index 6c1b17f62b7..17ca02d36c7 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -1,7 +1,6 @@
 /* Lisp parsing and input streams.
 
-Copyright (C) 1985-1989, 1993-1995, 1997-2013 Free Software Foundation,
-Inc.
+Copyright (C) 1985-1989, 1993-1995, 1997-2013 Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
 
@@ -4106,17 +4105,17 @@ defvar_kboard (struct Lisp_Kboard_Objfwd *ko_fwd,
   SET_SYMBOL_FWD (XSYMBOL (sym), (union Lisp_Fwd *)ko_fwd);
 }
 
-/* Check that the elements of Vload_path exist.  */
+/* Check that the elements of lpath exist.  */
 
 static void
-load_path_check (void)
+load_path_check (Lisp_Object lpath)
 {
   Lisp_Object path_tail;
 
   /* The only elements that might not exist are those from
      PATH_LOADSEARCH, EMACSLOADPATH.  Anything else is only added if
      it exists.  */
-  for (path_tail = Vload_path; !NILP (path_tail); path_tail = XCDR (path_tail))
+  for (path_tail = lpath; !NILP (path_tail); path_tail = XCDR (path_tail))
     {
       Lisp_Object dirfile;
       dirfile = Fcar (path_tail);
@@ -4133,19 +4132,23 @@ load_path_check (void)
    so we can see if the site changed it later during dumping.  */
 static Lisp_Object dump_path;
 
-/* Compute the default Vload_path, with the following logic:
-   If CANNOT_DUMP:
-   use EMACSLOADPATH env-var if set; otherwise use PATH_LOADSEARCH,
-   prepending PATH_SITELOADSEARCH unless --no-site-lisp.
+/* 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),
+   but it does (unless no_site_lisp is set) include site-lisp
+   directories in the source/build directories if those exist and we
+   are running uninstalled.
+
+   Uses the following logic:
+   If CANNOT_DUMP: Use PATH_LOADSEARCH.
    The remainder is what happens when dumping works:
    If purify-flag (ie dumping) just use PATH_DUMPLOADSEARCH.
-   Otherwise use EMACSLOADPATH if set, else PATH_LOADSEARCH.
+   Otherwise use PATH_LOADSEARCH.
 
-   If !initialized, then just set both Vload_path and dump_path.
-   If initialized, then if Vload_path != dump_path, do nothing.
+   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,
-   or because EMACSLOADPATH is set.)
+   This can only be from a site-load file during dumping.)
    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
@@ -4162,12 +4165,11 @@ static Lisp_Object dump_path;
    install-dir/src/Makefile.in does NOT exist (this is a sanity
    check), then repeat the above steps for source-dir/lisp,
    leim and site-lisp.
-   Finally, add the site-lisp directories at the front (if !no_site_lisp).
 */
-
-void
-init_lread (void)
+Lisp_Object
+load_path_default (bool ignore_existing)
 {
+  Lisp_Object lpath = Qnil;
   const char *normal;
 
 #ifdef CANNOT_DUMP
@@ -4177,35 +4179,14 @@ init_lread (void)
 
   normal = PATH_LOADSEARCH;
 #ifdef HAVE_NS
-  Vload_path = decode_env_path ("EMACSLOADPATH", loadpath ? loadpath : normal);
+  lpath = decode_env_path (0, loadpath ? loadpath : normal, 0);
 #else
-  Vload_path = decode_env_path ("EMACSLOADPATH", normal);
+  lpath = decode_env_path (0, normal, 0);
 #endif
 
-  load_path_check ();
-
-  /* FIXME CANNOT_DUMP platforms should get source-dir/lisp etc added
-   to their load-path too, AFAICS.  I don't think we can tell the
-   difference between initialized and !initialized in this case,
-   so we'll have to do it unconditionally when Vinstallation_directory
-   is non-nil.  */
-  if (!no_site_lisp && !egetenv ("EMACSLOADPATH"))
-    {
-      Lisp_Object sitelisp;
-      sitelisp = decode_env_path (0, PATH_SITELOADSEARCH);
-      if (! NILP (sitelisp)) Vload_path = nconc2 (sitelisp, Vload_path);
-    }
 #else  /* !CANNOT_DUMP */
-  if (NILP (Vpurify_flag))
-    {
-      normal = PATH_LOADSEARCH;
-      /* If the EMACSLOADPATH environment variable is set, use its value.
-         This doesn't apply if we're dumping.  */
-      if (egetenv ("EMACSLOADPATH"))
-        Vload_path = decode_env_path ("EMACSLOADPATH", normal);
-    }
-  else
-    normal = PATH_DUMPLOADSEARCH;
+
+  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
@@ -4216,24 +4197,22 @@ init_lread (void)
      site-lisp files that were processed during dumping.  */
   if (initialized)
     {
-      if (NILP (Fequal (dump_path, Vload_path)))
+      if (!ignore_existing && NILP (Fequal (dump_path, Vload_path)))
         {
-          /* Do not make any changes, just check the elements exist.  */
-          /* Note: --no-site-lisp is ignored.
-             I don't know what to do about this.  */
-          load_path_check ();
+          /* Do not make any changes.  */
+          return Vload_path;
         }
       else
-	{
+        {
 #ifdef HAVE_NS
-	  const char *loadpath = ns_load_path ();
-	  Vload_path = decode_env_path (0, loadpath ? loadpath : normal);
+          const char *loadpath = ns_load_path ();
+          lpath = decode_env_path (0, loadpath ? loadpath : normal, 0);
 #else
-	  Vload_path = decode_env_path (0, normal);
+          lpath = decode_env_path (0, normal, 0);
 #endif
-	  if (!NILP (Vinstallation_directory))
-	    {
-	      Lisp_Object tem, tem1;
+          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,
@@ -4243,19 +4222,19 @@ init_lread (void)
               tem1 = Ffile_accessible_directory_p (tem);
               if (!NILP (tem1))
                 {
-                  if (NILP (Fmember (tem, Vload_path)))
+                  if (NILP (Fmember (tem, lpath)))
                     {
                       /* We are running uninstalled.  The default load-path
                          points to the eventual installed lisp, leim
                          directories.  We should not use those now, even
                          if they exist, so start over from a clean slate.  */
-                      Vload_path = list1 (tem);
+                      lpath = list1 (tem);
                     }
                 }
               else
                 /* That dir doesn't exist, so add the build-time
                    Lisp dirs instead.  */
-                Vload_path = nconc2 (Vload_path, dump_path);
+                lpath = nconc2 (lpath, dump_path);
 
               /* Add leim under the installation dir, if it is accessible. */
               tem = Fexpand_file_name (build_string ("leim"),
@@ -4263,8 +4242,8 @@ init_lread (void)
               tem1 = Ffile_accessible_directory_p (tem);
               if (!NILP (tem1))
                 {
-                  if (NILP (Fmember (tem, Vload_path)))
-                    Vload_path = Fcons (tem, Vload_path);
+                  if (NILP (Fmember (tem, lpath)))
+                    lpath = Fcons (tem, lpath);
                 }
 
               /* Add site-lisp under the installation dir, if it exists.  */
@@ -4275,8 +4254,8 @@ init_lread (void)
                   tem1 = Ffile_accessible_directory_p (tem);
                   if (!NILP (tem1))
                     {
-                      if (NILP (Fmember (tem, Vload_path)))
-                        Vload_path = Fcons (tem, Vload_path);
+                      if (NILP (Fmember (tem, lpath)))
+                        lpath = Fcons (tem, lpath);
                     }
                 }
 
@@ -4304,14 +4283,14 @@ init_lread (void)
                       tem = Fexpand_file_name (build_string ("lisp"),
                                                Vsource_directory);
 
-                      if (NILP (Fmember (tem, Vload_path)))
-                        Vload_path = Fcons (tem, Vload_path);
+                      if (NILP (Fmember (tem, lpath)))
+                        lpath = Fcons (tem, lpath);
 
                       tem = Fexpand_file_name (build_string ("leim"),
                                                Vsource_directory);
 
-                      if (NILP (Fmember (tem, Vload_path)))
-                        Vload_path = Fcons (tem, Vload_path);
+                      if (NILP (Fmember (tem, lpath)))
+                        lpath = Fcons (tem, lpath);
 
                       if (!no_site_lisp)
                         {
@@ -4320,47 +4299,101 @@ init_lread (void)
                           tem1 = Ffile_accessible_directory_p (tem);
                           if (!NILP (tem1))
                             {
-                              if (NILP (Fmember (tem, Vload_path)))
-                                Vload_path = Fcons (tem, Vload_path);
+                              if (NILP (Fmember (tem, lpath)))
+                                lpath = Fcons (tem, lpath);
                             }
                         }
                     }
                 } /* Vinstallation_directory != Vsource_directory */
 
-	    } /* if Vinstallation_directory */
-
-          /* Check before adding the site-lisp directories.
-             The install should have created them, but they are not
-             required, so no need to warn if they are absent.
-             Or we might be running before installation.  */
-          load_path_check ();
+            } /* if Vinstallation_directory */
 
-          /* Add the site-lisp directories at the front.  */
-          if (!no_site_lisp)
-            {
-              Lisp_Object sitelisp;
-              sitelisp = decode_env_path (0, PATH_SITELOADSEARCH);
-              if (! NILP (sitelisp)) Vload_path = nconc2 (sitelisp, Vload_path);
-            }
-	} /* if dump_path == Vload_path */
+        } /* if dump_path == Vload_path */
     }
   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
+         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
          for Makefile.  */
-      Vload_path = decode_env_path (0, normal);
-      dump_path = Vload_path;
-      /* No point calling load_path_check; load-path only contains essential
-         elements from the source directory at this point.  They cannot
-         be missing unless something went extremely (and improbably)
-         wrong, in which case the build will fail in obvious ways.  */
+      lpath = decode_env_path (0, normal, 0);
+      dump_path = lpath;
     }
-#endif  /* !CANNOT_DUMP */
+#endif /* !CANNOT_DUMP */
+
+  return lpath;
+}
+
+void
+init_lread (void)
+{
+  /* First, set Vload_path.  */
+
+  /* We explicitly ignore EMACSLOADPATH when dumping.  */
+  if (NILP (Vpurify_flag) && egetenv ("EMACSLOADPATH"))
+    {
+      Vload_path = decode_env_path ("EMACSLOADPATH", 0, 1);
+
+      /* Check (non-nil) user-supplied elements.  */
+      load_path_check (Vload_path);
+
+      /* Replace any nil elements from the environment with the default.  */
+      if (Fmemq (Qnil, Vload_path))
+        {
+          Lisp_Object lpath = Vload_path;
+          Lisp_Object elem, default_lpath = load_path_default (1);
+
+          /* Check defaults, before adding site-lisp.  */
+          load_path_check (default_lpath);
+
+          /* Add the site-lisp directories to the front of the default.  */
+          if (!no_site_lisp)
+            {
+              Lisp_Object sitelisp;
+              sitelisp = decode_env_path (0, PATH_SITELOADSEARCH, 0);
+              if (! NILP (sitelisp))
+                default_lpath = nconc2 (sitelisp, default_lpath);
+            }
+
+          Vload_path = Qnil;
+
+          /* Replace nils from EMACSLOADPATH by default.  */
+          while (CONSP (lpath))
+            {
+              Lisp_Object arg[2];
+              elem = XCAR (lpath);
+              lpath = XCDR (lpath);
+              arg[0] = Vload_path;
+              arg[1] = NILP (elem) ? default_lpath : Fcons (elem, Qnil);
+              Vload_path = Fappend (2, arg);
+            }
+        }                       /* Fmemq (Qnil, Vload_path) */
+    }
+  else                          /* Vpurify_flag || !EMACSLOADPATH */
+    {
+      Vload_path = load_path_default (0);
+
+      /* Check before adding site-lisp directories.
+         The install should have created them, but they are not
+         required, so no need to warn if they are absent.
+         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 somehow already been changed (this can only be
+         from a site-load file during dumping?) from the dumped value.
+         FIXME?  Should we ignore any dump_path changes?  */
+      if (initialized && !no_site_lisp &&
+          ! NILP (Fequal (dump_path, Vload_path)))
+        {
+          Lisp_Object sitelisp;
+          sitelisp = decode_env_path (0, PATH_SITELOADSEARCH, 0);
+          if (! NILP (sitelisp)) Vload_path = nconc2 (sitelisp, Vload_path);
+        }
+    }                           /* !Vpurify_flag && EMACSLOADPATH */
 
   Vvalues = Qnil;
 
@@ -4467,9 +4500,8 @@ were read in.  */);
 
   DEFVAR_LISP ("load-path", Vload_path,
 	       doc: /* List of directories to search for files to load.
-Each element is a string (directory name) or nil (try default directory).
-Initialized based on EMACSLOADPATH environment variable, if any,
-otherwise to default specified by file `epaths.h' when Emacs was built.  */);
+Each element is a string (directory name) or nil (meaning `default-directory').
+Initialized during startup as described in Info node `(elisp)Library Search'.  */);
 
   DEFVAR_LISP ("load-suffixes", Vload_suffixes,
 	       doc: /* List of suffixes for (compiled or source) Emacs Lisp files.
@@ -4585,7 +4617,7 @@ and is not meant for users to change.  */);
 You cannot count on them to still be there!  */);
   Vsource_directory
     = Fexpand_file_name (build_string ("../"),
-			 Fcar (decode_env_path (0, PATH_DUMPLOADSEARCH)));
+			 Fcar (decode_env_path (0, PATH_DUMPLOADSEARCH, 0)));
 
   DEFVAR_LISP ("preloaded-file-list", Vpreloaded_file_list,
 	       doc: /* List of files that were preloaded (when dumping Emacs).  */);
diff --git a/test/ChangeLog b/test/ChangeLog
index 84c76c6d83b..59aacd13fd0 100644
--- a/test/ChangeLog
+++ b/test/ChangeLog
@@ -1,3 +1,8 @@
+2013-11-23  Glenn Morris  <rgm@gnu.org>
+
+	* automated/Makefile.in (emacs):
+	Empty EMACSLOADPATH rather than unsetting.
+
 2013-11-22  Glenn Morris  <rgm@gnu.org>
 
 	* automated/ruby-mode-tests.el (ruby-exit!-font-lock):
diff --git a/test/automated/Makefile.in b/test/automated/Makefile.in
index a8adaf40483..d187fa607b2 100644
--- a/test/automated/Makefile.in
+++ b/test/automated/Makefile.in
@@ -43,8 +43,7 @@ BYTE_COMPILE_EXTRA_FLAGS =
 
 # The actual Emacs command run in the targets below.
 # Prevent any setting of EMACSLOADPATH in user environment causing problems.
-emacs = unset EMACSLOADPATH; \
-	LC_ALL=C EMACS_TEST_DIRECTORY=$(srcdir) "$(EMACS)" $(EMACSOPT)
+emacs = EMACSLOADPATH= LC_ALL=C EMACS_TEST_DIRECTORY=$(srcdir) "$(EMACS)" $(EMACSOPT)
 
 # Common command to find subdirectories
 setwins=for file in `find $(srcdir) -type d -print`; do \