Fix 'expand-file-name' during startup on MS-Windows

* src/w32.c (w32_init_file_name_codepage): New function, resets
file_name_codepage and w32_ansi_code_page to undo the values
recorded during dumping.
(codepage_for_filenames): Fix an embarrassing typo.  Ignore the
cached value of file-name encoding if it is nil, i.e. not
initialized yet.  Actually cache the last used file-name encoding
to avoid calling APIs when not necessary.

* src/w32.h (w32_init_file_name_codepage): Add prototype.

* src/w32term.c (syms_of_w32term): Set the value of
w32_unicode_filenames according to the OS version.  This avoids
resetting it during startup, which then causes temacs to run with
the incorrect value.

* src/emacs.c (main): Call w32_init_file_name_codepage early
during the startup.

* src/fileio.c (Fexpand_file_name) [WINDOWSNT]: Update 'newdir'
after converting $HOME to a UTF-8 string, so that 'newdirlim' is
consistent with it.  (Bug#25038)

* lisp/international/mule-cmds.el (set-locale-environment): Set
'default-file-name-coding-system' to the ANSI codepage even in
non-interactive sessions.

* lisp/files.el (directory-abbrev-alist, abbreviated-home-dir):
Doc fix.
(abbreviate-file-name): Decode 'abbreviated-home-dir' if it is a
unibyte string.

* doc/lispref/files.texi (Directory Names): Index
'directory-abbrev-alist'.

5 files changed, 28 insertions, 7 deletions

diff --git a/src/emacs.c b/src/emacs.c
index ce30ae741b2..16cf6cc0e4d 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -716,6 +716,9 @@ main (int argc, char **argv)
      to have non-stub implementations of APIs we need to convert file
      names between UTF-8 and the system's ANSI codepage.  */
   maybe_load_unicows_dll ();
+  /* Initialize the codepage for file names, needed to decode
+     non-ASCII file names during startup.  */
+  w32_init_file_name_codepage ();
 #endif
   /* This has to be done before module_init is called below, so that
      the latter could use the thread ID of the main thread.  */
diff --git a/src/fileio.c b/src/fileio.c
index c3b2be7c5f7..d94805f316b 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -1063,8 +1063,6 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
           if (!(newdir = egetenv ("HOME")))
             newdir = newdirlim = "";
           nm++;
-          /* `egetenv' may return a unibyte string, which will bite us since
-             we expect the directory to be multibyte.  */
 #ifdef WINDOWSNT
           if (newdir[0])
             {
@@ -1072,11 +1070,14 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
 
               filename_from_ansi (newdir, newdir_utf8);
               tem = make_unibyte_string (newdir_utf8, strlen (newdir_utf8));
+              newdir = SSDATA (tem);
             }
           else
 #endif
             tem = build_string (newdir);
           newdirlim = newdir + SBYTES (tem);
+          /* `egetenv' may return a unibyte string, which will bite us
+             if we expect the directory to be multibyte.  */
           if (multibyte && !STRING_MULTIBYTE (tem))
             {
               hdir = DECODE_FILE (tem);
@@ -1105,8 +1106,7 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
 
               newdir = pw->pw_dir;
               /* `getpwnam' may return a unibyte string, which will
-                 bite us since we expect the directory to be
-                 multibyte.  */
+                 bite us when we expect the directory to be multibyte.  */
               tem = make_unibyte_string (newdir, strlen (newdir));
               newdirlim = newdir + SBYTES (tem);
               if (multibyte && !STRING_MULTIBYTE (tem))
diff --git a/src/w32.c b/src/w32.c
index 793bc0f28d0..7c57693cf3d 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -1493,6 +1493,16 @@ w32_valid_pointer_p (void *p, int size)
 /* Current codepage for encoding file names.  */
 static int file_name_codepage;
 
+/* Initialize the codepage used for decoding file names.  This is
+   needed to undo the value recorded during dumping, which might not
+   be correct when we run the dumped Emacs.  */
+void
+w32_init_file_name_codepage (void)
+{
+  file_name_codepage = CP_ACP;
+  w32_ansi_code_page = CP_ACP;
+}
+
 /* Produce a Windows ANSI codepage suitable for encoding file names.
    Return the information about that codepage in CP_INFO.  */
 int
@@ -1509,12 +1519,13 @@ codepage_for_filenames (CPINFO *cp_info)
   if (NILP (current_encoding))
     current_encoding = Vdefault_file_name_coding_system;
 
-  if (!EQ (last_file_name_encoding, current_encoding))
+  if (!EQ (last_file_name_encoding, current_encoding)
+      || NILP (last_file_name_encoding))
     {
       /* Default to the current ANSI codepage.  */
       file_name_codepage = w32_ansi_code_page;
 
-      if (NILP (current_encoding))
+      if (!NILP (current_encoding))
         {
           char *cpname = SSDATA (SYMBOL_NAME (current_encoding));
           char *cp = NULL, *end;
@@ -1543,6 +1554,9 @@ codepage_for_filenames (CPINFO *cp_info)
           if (!GetCPInfo (file_name_codepage, &cp))
             emacs_abort ();
         }
+
+      /* Cache the new value.  */
+      last_file_name_encoding = current_encoding;
     }
   if (cp_info)
     *cp_info = cp;
diff --git a/src/w32.h b/src/w32.h
index 42a1c423ce7..08b88f5f5a0 100644
--- a/src/w32.h
+++ b/src/w32.h
@@ -195,6 +195,7 @@ extern int  filename_from_ansi (const char *, char *);
 extern int  filename_to_ansi (const char *, char *);
 extern int  filename_from_utf16 (const wchar_t *, char *);
 extern int  filename_to_utf16 (const char *, wchar_t *);
+extern void w32_init_file_name_codepage (void);
 extern int  codepage_for_filenames (CPINFO *);
 extern Lisp_Object ansi_encode_filename (Lisp_Object);
 extern int  w32_copy_file (const char *, const char *, int, int, int);
diff --git a/src/w32term.c b/src/w32term.c
index 51743f8f94d..7b74ae03ad0 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -7157,7 +7157,10 @@ specified by `file-name-coding-system'.
 This variable is set to non-nil by default when Emacs runs on Windows
 systems of the NT family, including W2K, XP, Vista, Windows 7 and
 Windows 8.  It is set to nil on Windows 9X.  */);
-  w32_unicode_filenames = 0;
+  if (os_subtype == OS_9X)
+    w32_unicode_filenames = 0;
+  else
+    w32_unicode_filenames = 1;
 
 
   /* FIXME: The following variable will be (hopefully) removed