// (currently: during init), and not concurrent with DLL loading.
var IsSystemDLL = map[string]bool{}

// Add notes that dll is a system32 DLL which should only be loaded
// from the Windows SYSTEM32 directory. It returns its argument back,
// for ease of use in generated code.
func Add(dll string) string {
	IsSystemDLL[dll] = true
	return dll

// load system DLLs.
func LoadDLL(name string) (*DLL, error) {
	namep, err := UTF16PtrFromString(name)
	if err != nil {
		return nil, err
	}
	var h uintptr
	var e Errno
	if sysdll.IsSystemDLL[name] {
		h, e = loadsystemlibrary(namep)
	} else {
		h, e = loadlibrary(namep)
	}
	if e != 0 {
		return nil, &DLLError{
			Err:     e,
			ObjName: name,

	// silently downloaded some malicious DLLs.
	os.Chdir(tmpdir)

	// First before we can load a DLL from the current directory,
	// loading it only as "nojack.dll", without an absolute path.
	delete(sysdll.IsSystemDLL, name) // in case test was run repeatedly
	dll, err = syscall.LoadDLL(name)
	if err != nil {
		t.Fatalf("failed to load %s by base name before sysdll registration: %v", name, err)
	}
	dll.Release()