[newlib-cygwin] cygwin: unlink: fix "final trick" overwrite method on remote drives

[Corinna Vinschen <corinna at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=e6c79e7a2ab7fe9e1d45c25526841e035ee67407

commit e6c79e7a2ab7fe9e1d45c25526841e035ee67407
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Wed Oct 18 16:21:12 2017 +0200

    cygwin: unlink: fix "final trick" overwrite method on remote drives
    
    The "final trick" code in try_to_bin accidentally never worked on
    remote drives because it relies on rootdir.  Which isn't set for
    remote unlinks.  The code now creates a full path for remote files.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/syscalls.cc | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
index e64b017..8ccc768 100644
--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -542,8 +542,22 @@ try_to_bin (path_conv &pc, HANDLE &fh, ACCESS_MASK access, ULONG flags)
      delete-on-close on the original file succeeds.  There are still
      cases in which this fails, for instance, when trying to delete a
      hardlink to a DLL used by the unlinking application itself. */
-  RtlAppendUnicodeToString (&recycler, L"X");
-  InitializeObjectAttributes (&attr, &recycler, 0, rootdir, NULL);
+  if (pc.isremote ())
+    {
+      /* In the remote case we need the full path, but recycler is only
+	 a relative path.  Convert to absolute path. */
+      RtlInitEmptyUnicodeString (&fname, (PCWSTR) tp.w_get (),
+				 (NT_MAX_PATH - 1) * sizeof (WCHAR));
+      RtlCopyUnicodeString (&fname, pc.get_nt_native_path ());
+      RtlSplitUnicodePath (&fname, &fname, NULL);
+      /* Reset max length, overwritten by RtlSplitUnicodePath. */
+      fname.MaximumLength = (NT_MAX_PATH - 1) * sizeof (WCHAR); /* reset */
+      RtlAppendUnicodeStringToString (&fname, &recycler);
+    }
+  else
+    fname = recycler;
+  RtlAppendUnicodeToString (&fname, L"X");
+  InitializeObjectAttributes (&attr, &fname, 0, rootdir, NULL);
   status = NtCreateFile (&tmp_fh, DELETE, &attr, &io, NULL,
 			 FILE_ATTRIBUTE_NORMAL, 0, FILE_SUPERSEDE,
 			 FILE_NON_DIRECTORY_FILE | FILE_DELETE_ON_CLOSE,