MessageBoxA

// USER32.dll  (ANSI / -A)
#include <windows.h>

MESSAGEBOX_RESULT MessageBoxA(
    HWND hWnd,   // optional
    LPCSTR lpText,   // optional
    LPCSTR lpCaption,   // optional
    MESSAGEBOX_STYLE uType
);

<DllImport("USER32.dll", CharSet:=CharSet.Ansi, SetLastError:=True, ExactSpelling:=True)>
Public Shared Function MessageBoxA(
    hWnd As IntPtr,   ' HWND optional
    <MarshalAs(UnmanagedType.LPStr)> lpText As String,   ' LPCSTR optional
    <MarshalAs(UnmanagedType.LPStr)> lpCaption As String,   ' LPCSTR optional
    uType As UInteger   ' MESSAGEBOX_STYLE
) As Integer
End Function

' hWnd : HWND optional
' lpText : LPCSTR optional
' lpCaption : LPCSTR optional
' uType : MESSAGEBOX_STYLE
Declare PtrSafe Function MessageBoxA Lib "user32" ( _
    ByVal hWnd As LongPtr, _
    ByVal lpText As String, _
    ByVal lpCaption As String, _
    ByVal uType As Long) As Long
' VBA7前提(PtrSafe)。32bit Office では LongPtr→Long。Integer=16bit / Long=32bit / LongLong=64bit。

import ctypes
from ctypes import wintypes

MessageBoxA = ctypes.windll.user32.MessageBoxA
MessageBoxA.restype = ctypes.c_int
MessageBoxA.argtypes = [
    wintypes.HANDLE,  # hWnd : HWND optional
    wintypes.LPCSTR,  # lpText : LPCSTR optional
    wintypes.LPCSTR,  # lpCaption : LPCSTR optional
    wintypes.DWORD,  # uType : MESSAGEBOX_STYLE
]
# GetLastError: use ctypes.GetLastError() (or ctypes.WinDLL(use_last_error=True))

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('USER32.dll')
MessageBoxA = Fiddle::Function.new(
  lib['MessageBoxA'],
  [
    Fiddle::TYPE_VOIDP,  # hWnd : HWND optional
    Fiddle::TYPE_VOIDP,  # lpText : LPCSTR optional
    Fiddle::TYPE_VOIDP,  # lpCaption : LPCSTR optional
    -Fiddle::TYPE_INT,  # uType : MESSAGEBOX_STYLE
  ],
  Fiddle::TYPE_INT)

#[link(name = "user32")]
extern "system" {
    fn MessageBoxA(
        hWnd: *mut core::ffi::c_void,  // HWND optional
        lpText: *const u8,  // LPCSTR optional
        lpCaption: *const u8,  // LPCSTR optional
        uType: u32  // MESSAGEBOX_STYLE
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("USER32.dll", CharSet = CharSet.Ansi, SetLastError = true)]
public static extern int MessageBoxA(IntPtr hWnd, [MarshalAs(UnmanagedType.LPStr)] string lpText, [MarshalAs(UnmanagedType.LPStr)] string lpCaption, uint uType);
"@
$api = Add-Type -MemberDefinition $sig -Name 'USER32_MessageBoxA' -Namespace Win32 -PassThru
# $api::MessageBoxA(hWnd, lpText, lpCaption, uType)

#uselib "USER32.dll"
#func global MessageBoxA "MessageBoxA" sptr, sptr, sptr, sptr
; MessageBoxA hWnd, lpText, lpCaption, uType   ; 戻り値は stat
; hWnd : HWND optional -> "sptr"
; lpText : LPCSTR optional -> "sptr"
; lpCaption : LPCSTR optional -> "sptr"
; uType : MESSAGEBOX_STYLE -> "sptr"
; ※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 "USER32.dll"
#cfunc global MessageBoxA "MessageBoxA" sptr, str, str, int
; res = MessageBoxA(hWnd, lpText, lpCaption, uType)
; hWnd : HWND optional -> "sptr"
; lpText : LPCSTR optional -> "str"
; lpCaption : LPCSTR optional -> "str"
; uType : MESSAGEBOX_STYLE -> "int"

; MESSAGEBOX_RESULT MessageBoxA(HWND hWnd, LPCSTR lpText, LPCSTR lpCaption, MESSAGEBOX_STYLE uType)
#uselib "USER32.dll"
#cfunc global MessageBoxA "MessageBoxA" intptr, str, str, int
; res = MessageBoxA(hWnd, lpText, lpCaption, uType)
; hWnd : HWND optional -> "intptr"
; lpText : LPCSTR optional -> "str"
; lpCaption : LPCSTR optional -> "str"
; uType : MESSAGEBOX_STYLE -> "int"

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

var (
	user32 = windows.NewLazySystemDLL("USER32.dll")
	procMessageBoxA = user32.NewProc("MessageBoxA")
)

// hWnd (HWND optional), lpText (LPCSTR optional), lpCaption (LPCSTR optional), uType (MESSAGEBOX_STYLE)
r1, _, err := procMessageBoxA.Call(
	uintptr(hWnd),
	uintptr(unsafe.Pointer(windows.BytePtrFromString(lpText))),
	uintptr(unsafe.Pointer(windows.BytePtrFromString(lpCaption))),
	uintptr(uType),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // MESSAGEBOX_RESULT

function MessageBoxA(
  hWnd: THandle;   // HWND optional
  lpText: PAnsiChar;   // LPCSTR optional
  lpCaption: PAnsiChar;   // LPCSTR optional
  uType: DWORD   // MESSAGEBOX_STYLE
): Integer; stdcall;
  external 'USER32.dll' name 'MessageBoxA';

result := DllCall("USER32\MessageBoxA"
    , "Ptr", hWnd   ; HWND optional
    , "AStr", lpText   ; LPCSTR optional
    , "AStr", lpCaption   ; LPCSTR optional
    , "UInt", uType   ; MESSAGEBOX_STYLE
    , "Int")   ; return: MESSAGEBOX_RESULT

●MessageBoxA(hWnd, lpText, lpCaption, uType) = DLL("USER32.dll", "int MessageBoxA(void*, char*, char*, dword)")
# 呼び出し: MessageBoxA(hWnd, lpText, lpCaption, uType)
# hWnd : HWND optional -> "void*"
# lpText : LPCSTR optional -> "char*"
# lpCaption : LPCSTR optional -> "char*"
# uType : MESSAGEBOX_STYLE -> "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)。