No effect of SE_BACKUP_NAME privilege on cygwin?

[Christian Franke <Christian dot Franke at t-online dot de>]

Enabling SE_BACKUP_NAME has no effect for cygwin programs.

The attached program demonstrates the issue.
It retrieves the attributes of a normally inaccessible file without and 
with SE_BACKUP_NAME.
(The file should be present on XP with C:\ as system drive)

If compiled with "-mno-cygwin" and running as admin on XP Prof, the 
second access succeeds as expected:

GetFileAttributes failed: 5
SeBackupPrivilege enabled!
GetFileAttributes = 0x0026

But if running as a cygwin program on 1.5.19, the result is:

GetFileAttributes failed: 5
SeBackupPrivilege enabled!
GetFileAttributes failed: 5

The privilege can be enabled, but has no effect - bug or feature ?-)

Thanks for any help.

Christian

#include <windows.h>
#include <stdio.h>

static void Check()
{
	DWORD attr = GetFileAttributes("C:/System Volume Information/MountPointManagerRemoteDatabase");
	if (attr == ~(DWORD)0)
		printf("GetFileAttributes failed: %ld\n", GetLastError());
	else
		printf("GetFileAttributes = 0x%04lx\n", attr); // Usually 0x0026, Archive|System|Hidden
}

static bool GetBackupPrivil()
{
	HANDLE t;
	if(!OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES, &t)) {
		printf("OpenProcessToken failed: %ld\n", GetLastError()); return false;
	}
	TOKEN_PRIVILEGES tp;
	if(!LookupPrivilegeValue(NULL, SE_BACKUP_NAME, &tp.Privileges[0].Luid)) {
		printf("LookupPrivilegeValue failed: %ld\n", GetLastError()); return false;
	}
	tp.PrivilegeCount           = 1;
	tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
	AdjustTokenPrivileges(t, FALSE, &tp, 0, NULL, NULL);
	if (GetLastError() != ERROR_SUCCESS) {
		printf("AdjustTokenPrivileges failed: %ld\n", GetLastError()); return false;
	}
	CloseHandle(t);
	printf(SE_BACKUP_NAME" enabled!\n");
	return true;
}

main()
{
	Check();

	if (!GetBackupPrivil())
		return 1;

	Check();
	return 0;
}

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