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'.

1 files changed, 16 insertions, 2 deletions

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;