Fix bug #12587 with slow startup on MS-Windows with Netlogon service.

 src/fileio.c (check_existing): New function.
 (make_temp_name, Ffile_exists_p, Ffile_writable_p): Call it
 instead of calling 'stat', when what's needed is to check whether
 a file exists.  This avoids expensive system calls on MS-Windows.
 src/w32.c (init_environment): Call 'check_existing' instead of 'stat'.
 src/lread.c (openp) [WINDOWSNT]: Call 'access' instead of 'stat' to
 determine whether a file exists and is not a directory.
 src/lisp.h (check_existing): Add prototype.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/lread.c b/src/lread.c
index dbbde694cf6..6d4c0d990af 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -1449,7 +1449,6 @@ openp (Lisp_Object path, Lisp_Object str, Lisp_Object suffixes, Lisp_Object *sto
   bool absolute = 0;
   ptrdiff_t want_length;
   Lisp_Object filename;
-  struct stat st;
   struct gcpro gcpro1, gcpro2, gcpro3, gcpro4, gcpro5, gcpro6;
   Lisp_Object string, tail, encoded_fn;
   ptrdiff_t max_suffix_len = 0;
@@ -1543,11 +1542,18 @@ openp (Lisp_Object path, Lisp_Object str, Lisp_Object suffixes, Lisp_Object *sto
             }
           else
             {
+#ifndef WINDOWSNT
+              struct stat st;
+#endif
               const char *pfn;
 
               encoded_fn = ENCODE_FILE (string);
               pfn = SSDATA (encoded_fn);
+#ifdef WINDOWSNT
+              exists = access (pfn, F_OK) == 0 && access (pfn, D_OK) < 0;
+#else
               exists = (stat (pfn, &st) == 0 && ! S_ISDIR (st.st_mode));
+#endif
               if (exists)
                 {
                   /* Check that we can access or open it.  */