MS-Windows followup for 2012-11-14T04:55:41Z!eggert@cs.ucla.edu, regarding faccessat.

 nt/inc/unistd.h (faccessat): Add prototype.
 (AT_FDCWD, AT_EACCESS, AT_SYMLINK_NOFOLLOW): New macros; the first
 2 moved from ms-w32.h.
 nt/inc/ms-w32.h (AT_FDCWD, AT_EACCESS, faccessat): Remove macros.

 src/w32.c (faccessat): Rename from sys_faccessat.  (No need to use a
 different name, as the MS runtime does not have such a function,
 and probably never will.)  All callers changed.  Ignore DIRFD
 value if PATH is an absolute file name, to match Posix spec
 better.  If AT_SYMLINK_NOFOLLOW is set in FLAGS, don't resolve
 symlinks.

Fixes: debbugs:12632

2 files changed, 26 insertions, 13 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 99f3128b321..ec8f7e219f7 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2012-11-14  Eli Zaretskii  <eliz@gnu.org>
+
+        * w32.c (faccessat): Rename from sys_faccessat.  (No need to use a
+        different name, as the MS runtime does not have such a function,
+        and probably never will.)  All callers changed.  Ignore DIRFD
+        value if PATH is an absolute file name, to match Posix spec
+        better.  If AT_SYMLINK_NOFOLLOW is set in FLAGS, don't resolve
+        symlinks.
+
 2012-11-14  Dmitry Antipov  <dmantipov@yandex.ru>
 
         * xdisp.c (echo_area_display, redisplay_internal):
diff --git a/src/w32.c b/src/w32.c
index 0e7da449b81..eb07e13a2fb 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -1597,7 +1597,7 @@ init_environment (char ** argv)
          see if it succeeds.  But I think that's too much to ask.  */
 
       /* MSVCRT's _access crashes with D_OK.  */
-      if (tmp && sys_faccessat (AT_FDCWD, tmp, D_OK, AT_EACCESS) == 0)
+      if (tmp && faccessat (AT_FDCWD, tmp, D_OK, AT_EACCESS) == 0)
         {
           char * var = alloca (strlen (tmp) + 8);
           sprintf (var, "TMPDIR=%s", tmp);
@@ -2708,17 +2708,15 @@ logon_network_drive (const char *path)
   WNetAddConnection2 (&resource, NULL, NULL, CONNECT_INTERACTIVE);
 }
 
-/* Shadow some MSVC runtime functions to map requests for long filenames
-   to reasonable short names if necessary.  This was originally added to
-   permit running Emacs on NT 3.1 on a FAT partition, which doesn't support
-   long file names.  */
-
+/* Emulate faccessat(2).  */
 int
-sys_faccessat (int dirfd, const char * path, int mode, int flags)
+faccessat (int dirfd, const char * path, int mode, int flags)
 {
   DWORD attributes;
 
-  if (dirfd != AT_FDCWD)
+  if (dirfd != AT_FDCWD
+      && !(IS_DIRECTORY_SEP (path[0])
+           || IS_DEVICE_SEP (path[1])))
     {
       errno = EBADF;
       return -1;
@@ -2731,7 +2729,8 @@ sys_faccessat (int dirfd, const char * path, int mode, int flags)
      to get the attributes of its target file.  Note: any symlinks in
      PATH elements other than the last one are transparently resolved
      by GetFileAttributes below.  */
-  if ((volume_info.flags & FILE_SUPPORTS_REPARSE_POINTS) != 0)
+  if ((volume_info.flags & FILE_SUPPORTS_REPARSE_POINTS) != 0
+      && (flags & AT_SYMLINK_NOFOLLOW) == 0)
     path = chase_symlinks (path);
 
   if ((attributes = GetFileAttributes (path)) == -1)
@@ -2781,6 +2780,11 @@ sys_faccessat (int dirfd, const char * path, int mode, int flags)
   return 0;
 }
 
+/* Shadow some MSVC runtime functions to map requests for long filenames
+   to reasonable short names if necessary.  This was originally added to
+   permit running Emacs on NT 3.1 on a FAT partition, which doesn't support
+   long file names.  */
+
 int
 sys_chdir (const char * path)
 {
@@ -2966,7 +2970,7 @@ sys_mktemp (char * template)
         {
           int save_errno = errno;
           p[0] = first_char[i];
-          if (sys_faccessat (AT_FDCWD, template, F_OK, AT_EACCESS) < 0)
+          if (faccessat (AT_FDCWD, template, F_OK, AT_EACCESS) < 0)
             {
               errno = save_errno;
               return template;
@@ -4017,7 +4021,7 @@ symlink (char const *filename, char const *linkname)
     {
       /* Non-absolute FILENAME is understood as being relative to
          LINKNAME's directory.  We need to prepend that directory to
-         FILENAME to get correct results from sys_faccessat below, since
+         FILENAME to get correct results from faccessat below, since
          otherwise it will interpret FILENAME relative to the
          directory where the Emacs process runs.  Note that
          make-symbolic-link always makes sure LINKNAME is a fully
@@ -4031,10 +4035,10 @@ symlink (char const *filename, char const *linkname)
         strncpy (tem, linkfn, p - linkfn);
       tem[p - linkfn] = '\0';
       strcat (tem, filename);
-      dir_access = sys_faccessat (AT_FDCWD, tem, D_OK, AT_EACCESS);
+      dir_access = faccessat (AT_FDCWD, tem, D_OK, AT_EACCESS);
     }
   else
-    dir_access = sys_faccessat (AT_FDCWD, filename, D_OK, AT_EACCESS);
+    dir_access = faccessat (AT_FDCWD, filename, D_OK, AT_EACCESS);
 
   /* Since Windows distinguishes between symlinks to directories and
      to files, we provide a kludgy feature: if FILENAME doesn't