From c3f0489235f6d0e9cf9d6c302d7b086b4f9968dc Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Sat, 28 Apr 2018 22:25:21 +0300
Subject: Fix try_rmfile() to remove symlinks on Windows

---
 libbutl/filesystem.cxx | 33 ++++++++++++++++++++++++---------
 libbutl/filesystem.mxx |  3 +++
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/libbutl/filesystem.cxx b/libbutl/filesystem.cxx
index bff251a..2650c25 100644
--- a/libbutl/filesystem.cxx
+++ b/libbutl/filesystem.cxx
@@ -322,19 +322,34 @@ namespace butl
     // error code. In such a case we just reset the attribute and repeat the
     // attempt. If the attempt fails, then we try to restore the attribute.
     //
+    // Yet another reason for the 'permission denied' failure can be a
+    // directory symlink.
+    //
     if (ur != 0 && errno == EACCES)
     {
       DWORD a (GetFileAttributes (f));
-      if (a != INVALID_FILE_ATTRIBUTES && (a & FILE_ATTRIBUTE_READONLY) != 0 &&
-          SetFileAttributes (f, a & ~FILE_ATTRIBUTE_READONLY))
+      if (a != INVALID_FILE_ATTRIBUTES)
       {
-        ur = _unlink (f);
+        bool readonly ((a & FILE_ATTRIBUTE_READONLY) != 0);
 
-        // Restoring the attribute is unlikely to fail as we managed to reset
-        // it earlier.
+        // Note that we support only directory symlinks on Windows.
         //
-        if (ur != 0)
-          SetFileAttributes (f, a);
+        bool symlink ((a & FILE_ATTRIBUTE_REPARSE_POINT) != 0 &&
+                      (a & FILE_ATTRIBUTE_DIRECTORY) != 0);
+
+        if (readonly || symlink)
+        {
+          bool restore (readonly &&
+                        SetFileAttributes (f, a & ~FILE_ATTRIBUTE_READONLY));
+
+          ur = symlink ? _rmdir (f) : _unlink (f);
+
+          // Restoring the attribute is unlikely to fail as we managed to reset
+          // it earlier.
+          //
+          if (ur != 0 && restore)
+            SetFileAttributes (f, a);
+        }
       }
     }
 #endif
@@ -492,8 +507,8 @@ namespace butl
           FSCTL_SET_REPARSE_POINT,
           &rb,
           sizeof (DWORD) + 2 * sizeof (WORD) + // Size of the header.
-          rb.reparse_data_length,              // Size of mount point reparse.
-          NULL,                                // buffer.
+          rb.reparse_data_length,              // Size of the mount point
+          NULL,                                // reparse buffer.
           0,
           &r,
           NULL))
diff --git a/libbutl/filesystem.mxx b/libbutl/filesystem.mxx
index fbfc0aa..ff9a4a6 100644
--- a/libbutl/filesystem.mxx
+++ b/libbutl/filesystem.mxx
@@ -194,6 +194,9 @@ LIBBUTL_MODEXPORT namespace butl
   // it does not exist. Unless ignore_error is true, all other
   // errors are reported by throwing std::system_error.
   //
+  // Note that if it is known that the path refers to a symlink, then usage of
+  // try_rmsymlink() function must be preferred, as a more efficient one.
+  //
   enum class rmfile_status {success, not_exist};
 
   // Note that on Windows the read-only attribute is reset prior to the file
-- 
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