Fix incompatbilities with MS-Windows 2000 and older

* src/w32.c <multiByteToWideCharFlags>: New global variable.
(filename_to_utf16, filename_from_ansi, check_windows_init_file):
Use it instead of the literal MB_ERR_INVALID_CHARS.
(maybe_load_unicows_dll): Initialize multiByteToWideCharFlags as
appropriate for the underlying OS version.  For details, see
http://lists.gnu.org/archive/html/emacs-devel/2016-01/msg00835.html.
* src/w32.h: Declare multiByteToWideCharFlags.
* src/w32fns.c (Fx_file_dialog, Fw32_shell_execute)
(add_tray_notification): Use multiByteToWideCharFlags instead of
the literal MB_ERR_INVALID_CHARS.
(_resetstkoflw_proc): New typedef.
(w32_reset_stack_overflow_guard): Call _resetstkoflw via a
pointer, as this function is absent in msvcrt.dll shipped with W2K
and older systems.

Copyright-paperwork-exempt: yes

1 files changed, 15 insertions, 8 deletions

diff --git a/src/w32.c b/src/w32.c
index 7884bad619c..6f1d5fd1698 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -486,6 +486,7 @@ typedef DWORD (WINAPI *GetAdaptersInfo_Proc) (
 
 int (WINAPI *pMultiByteToWideChar)(UINT,DWORD,LPCSTR,int,LPWSTR,int);
 int (WINAPI *pWideCharToMultiByte)(UINT,DWORD,LPCWSTR,int,LPSTR,int,LPCSTR,LPBOOL);
+DWORD multiByteToWideCharFlags;
 
   /* ** A utility function ** */
 static BOOL
@@ -1552,8 +1553,8 @@ codepage_for_filenames (CPINFO *cp_info)
 int
 filename_to_utf16 (const char *fn_in, wchar_t *fn_out)
 {
-  int result = pMultiByteToWideChar (CP_UTF8, MB_ERR_INVALID_CHARS, fn_in, -1,
-                                     fn_out, MAX_PATH);
+  int result = pMultiByteToWideChar (CP_UTF8, multiByteToWideCharFlags, fn_in,
+                                     -1, fn_out, MAX_PATH);
 
   if (!result)
     {
@@ -1643,8 +1644,8 @@ filename_from_ansi (const char *fn_in, char *fn_out)
 {
   wchar_t fn_utf16[MAX_PATH];
   int codepage = codepage_for_filenames (NULL);
-  int result = pMultiByteToWideChar (codepage, MB_ERR_INVALID_CHARS, fn_in, -1,
-                                     fn_utf16, MAX_PATH);
+  int result = pMultiByteToWideChar (codepage, multiByteToWideCharFlags, fn_in,
+                                     -1, fn_utf16, MAX_PATH);
 
   if (!result)
     {
@@ -9134,14 +9135,14 @@ check_windows_init_file (void)
                    "not unpacked properly.\nSee the README.W32 file in the "
                    "top-level Emacs directory for more information.",
                    init_file_name, load_path);
-          needed = pMultiByteToWideChar (CP_UTF8, MB_ERR_INVALID_CHARS, buffer,
-                                         -1, NULL, 0);
+          needed = pMultiByteToWideChar (CP_UTF8, multiByteToWideCharFlags,
+                                         buffer, -1, NULL, 0);
           if (needed > 0)
             {
               wchar_t *msg_w = alloca ((needed + 1) * sizeof (wchar_t));
 
-              pMultiByteToWideChar (CP_UTF8, MB_ERR_INVALID_CHARS, buffer, -1,
-                                    msg_w, needed);
+              pMultiByteToWideChar (CP_UTF8, multiByteToWideCharFlags, buffer,
+                                    -1, msg_w, needed);
               needed = pWideCharToMultiByte (CP_ACP, 0, msg_w, -1,
                                              NULL, 0, NULL, NULL);
               if (needed > 0)
@@ -9328,6 +9329,7 @@ maybe_load_unicows_dll (void)
             (MultiByteToWideChar_Proc)GetProcAddress (ret, "MultiByteToWideChar");
           pWideCharToMultiByte =
             (WideCharToMultiByte_Proc)GetProcAddress (ret, "WideCharToMultiByte");
+          multiByteToWideCharFlags = MB_ERR_INVALID_CHARS;
           return ret;
         }
       else
@@ -9357,6 +9359,11 @@ maybe_load_unicows_dll (void)
          pointers; no need for the LoadLibrary dance.  */
       pMultiByteToWideChar = MultiByteToWideChar;
       pWideCharToMultiByte = WideCharToMultiByte;
+      /* On NT 4.0, though, MB_ERR_INVALID_CHARS is not supported.  */
+      if (w32_major_version < 5)
+        multiByteToWideCharFlags = 0;
+      else
+        multiByteToWideCharFlags = MB_ERR_INVALID_CHARS;
       return LoadLibrary ("Gdi32.dll");
     }
 }