(Fexpand_file_name) [WINDOWSNT]: Be careful not to

concatenate the directory prefix and file name to accidentally
create a network share name.

1 files changed, 12 insertions, 1 deletions

diff --git a/src/fileio.c b/src/fileio.c
index 352129a0853..aef7a01e0a3 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -1419,7 +1419,18 @@ See also the function `substitute-in-file-name'.")
     {
 #ifndef VMS
       if (nm[0] == 0 || IS_DIRECTORY_SEP (nm[0]))
-        strcpy (target, newdir);
+        {
+#ifdef WINDOWSNT
+          /* If newdir is effectively "C:/", then the drive letter will have
+             been stripped and newdir will be "/".  Concatenating with an
+             absolute directory in nm produces "//", which will then be
+             incorrectly treated as a network share.  Ignore newdir in
+             this case (keeping the drive letter).  */
+          if (!(drive && nm[0] && IS_DIRECTORY_SEP (newdir[0]) 
+                && newdir[1] == '\0'))
+#endif
+            strcpy (target, newdir);
+        }
       else
 #endif
         file_name_as_directory (target, newdir);