RegSaveKeyExW

// ADVAPI32.dll  (Unicode / -W)
#include <windows.h>

WIN32_ERROR RegSaveKeyExW(
    HKEY hKey,
    LPCWSTR lpFile,
    const SECURITY_ATTRIBUTES* lpSecurityAttributes,   // optional
    REG_SAVE_FORMAT Flags
);

<DllImport("ADVAPI32.dll", CharSet:=CharSet.Unicode, ExactSpelling:=True)>
Public Shared Function RegSaveKeyExW(
    hKey As IntPtr,   ' HKEY
    <MarshalAs(UnmanagedType.LPWStr)> lpFile As String,   ' LPCWSTR
    lpSecurityAttributes As IntPtr,   ' SECURITY_ATTRIBUTES* optional
    Flags As UInteger   ' REG_SAVE_FORMAT
) As UInteger
End Function

' hKey : HKEY
' lpFile : LPCWSTR
' lpSecurityAttributes : SECURITY_ATTRIBUTES* optional
' Flags : REG_SAVE_FORMAT
Declare PtrSafe Function RegSaveKeyExW Lib "advapi32" ( _
    ByVal hKey As LongPtr, _
    ByVal lpFile As LongPtr, _
    ByVal lpSecurityAttributes As LongPtr, _
    ByVal Flags As Long) As Long
' Unicode(W): 文字列は ByVal As LongPtr とし StrPtr(unicodeStr) を渡す
' VBA7前提(PtrSafe)。32bit Office では LongPtr→Long。Integer=16bit / Long=32bit / LongLong=64bit。

import ctypes
from ctypes import wintypes

RegSaveKeyExW = ctypes.windll.advapi32.RegSaveKeyExW
RegSaveKeyExW.restype = wintypes.DWORD
RegSaveKeyExW.argtypes = [
    wintypes.HANDLE,  # hKey : HKEY
    wintypes.LPCWSTR,  # lpFile : LPCWSTR
    ctypes.c_void_p,  # lpSecurityAttributes : SECURITY_ATTRIBUTES* optional
    wintypes.DWORD,  # Flags : REG_SAVE_FORMAT
]

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('ADVAPI32.dll')
RegSaveKeyExW = Fiddle::Function.new(
  lib['RegSaveKeyExW'],
  [
    Fiddle::TYPE_VOIDP,  # hKey : HKEY
    Fiddle::TYPE_VOIDP,  # lpFile : LPCWSTR
    Fiddle::TYPE_VOIDP,  # lpSecurityAttributes : SECURITY_ATTRIBUTES* optional
    -Fiddle::TYPE_INT,  # Flags : REG_SAVE_FORMAT
  ],
  -Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "advapi32")]
extern "system" {
    fn RegSaveKeyExW(
        hKey: *mut core::ffi::c_void,  // HKEY
        lpFile: *const u16,  // LPCWSTR
        lpSecurityAttributes: *const SECURITY_ATTRIBUTES,  // SECURITY_ATTRIBUTES* optional
        Flags: u32  // REG_SAVE_FORMAT
    ) -> u32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("ADVAPI32.dll", CharSet = CharSet.Unicode)]
public static extern uint RegSaveKeyExW(IntPtr hKey, [MarshalAs(UnmanagedType.LPWStr)] string lpFile, IntPtr lpSecurityAttributes, uint Flags);
"@
$api = Add-Type -MemberDefinition $sig -Name 'ADVAPI32_RegSaveKeyExW' -Namespace Win32 -PassThru
# $api::RegSaveKeyExW(hKey, lpFile, lpSecurityAttributes, Flags)

#uselib "ADVAPI32.dll"
#func global RegSaveKeyExW "RegSaveKeyExW" wptr, wptr, wptr, wptr
; RegSaveKeyExW hKey, lpFile, varptr(lpSecurityAttributes), Flags   ; 戻り値は stat
; hKey : HKEY -> "wptr"
; lpFile : LPCWSTR -> "wptr"
; lpSecurityAttributes : SECURITY_ATTRIBUTES* optional -> "wptr"
; Flags : REG_SAVE_FORMAT -> "wptr"
; ※HSP3.7は #func のため戻り値はシステム変数 stat に格納されます。

#uselib "ADVAPI32.dll"
#cfunc global RegSaveKeyExW "RegSaveKeyExW" sptr, wstr, var, int
; res = RegSaveKeyExW(hKey, lpFile, lpSecurityAttributes, Flags)
; hKey : HKEY -> "sptr"
; lpFile : LPCWSTR -> "wstr"
; lpSecurityAttributes : SECURITY_ATTRIBUTES* optional -> "var"
; Flags : REG_SAVE_FORMAT -> "int"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。

; WIN32_ERROR RegSaveKeyExW(HKEY hKey, LPCWSTR lpFile, SECURITY_ATTRIBUTES* lpSecurityAttributes, REG_SAVE_FORMAT Flags)
#uselib "ADVAPI32.dll"
#cfunc global RegSaveKeyExW "RegSaveKeyExW" intptr, wstr, var, int
; res = RegSaveKeyExW(hKey, lpFile, lpSecurityAttributes, Flags)
; hKey : HKEY -> "intptr"
; lpFile : LPCWSTR -> "wstr"
; lpSecurityAttributes : SECURITY_ATTRIBUTES* optional -> "var"
; Flags : REG_SAVE_FORMAT -> "int"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。

import (
	"golang.org/x/sys/windows"
	"unsafe"
)

var (
	advapi32 = windows.NewLazySystemDLL("ADVAPI32.dll")
	procRegSaveKeyExW = advapi32.NewProc("RegSaveKeyExW")
)

// hKey (HKEY), lpFile (LPCWSTR), lpSecurityAttributes (SECURITY_ATTRIBUTES* optional), Flags (REG_SAVE_FORMAT)
r1, _, err := procRegSaveKeyExW.Call(
	uintptr(hKey),
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(lpFile))),
	uintptr(lpSecurityAttributes),
	uintptr(Flags),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // WIN32_ERROR

function RegSaveKeyExW(
  hKey: THandle;   // HKEY
  lpFile: PWideChar;   // LPCWSTR
  lpSecurityAttributes: Pointer;   // SECURITY_ATTRIBUTES* optional
  Flags: DWORD   // REG_SAVE_FORMAT
): DWORD; stdcall;
  external 'ADVAPI32.dll' name 'RegSaveKeyExW';

result := DllCall("ADVAPI32\RegSaveKeyExW"
    , "Ptr", hKey   ; HKEY
    , "WStr", lpFile   ; LPCWSTR
    , "Ptr", lpSecurityAttributes   ; SECURITY_ATTRIBUTES* optional
    , "UInt", Flags   ; REG_SAVE_FORMAT
    , "UInt")   ; return: WIN32_ERROR

●RegSaveKeyExW(hKey, lpFile, lpSecurityAttributes, Flags) = DLL("ADVAPI32.dll", "dword RegSaveKeyExW(void*, char*, void*, dword)")
# 呼び出し: RegSaveKeyExW(hKey, lpFile, lpSecurityAttributes, Flags)
# hKey : HKEY -> "void*"
# lpFile : LPCWSTR -> "char*"
# lpSecurityAttributes : SECURITY_ATTRIBUTES* optional -> "void*"
# Flags : REG_SAVE_FORMAT -> "dword"
# なでしこ1は32bit・ANSI(Shift_JIS)。文字列=char*(ANSI)、ポインタ/ハンドル=void*(4byte)。
# ※-W(Unicode)関数。なでしこ1はANSIのため -A 版の利用を推奨。