GetSystemDirectoryA

// KERNEL32.dll  (ANSI / -A)
#include <windows.h>

DWORD GetSystemDirectoryA(
    LPSTR lpBuffer,   // optional
    DWORD uSize
);

<DllImport("KERNEL32.dll", CharSet:=CharSet.Ansi, SetLastError:=True, ExactSpelling:=True)>
Public Shared Function GetSystemDirectoryA(
    <MarshalAs(UnmanagedType.LPStr)> lpBuffer As System.Text.StringBuilder,   ' LPSTR optional, out
    uSize As UInteger   ' DWORD
) As UInteger
End Function

' lpBuffer : LPSTR optional, out
' uSize : DWORD
Declare PtrSafe Function GetSystemDirectoryA Lib "kernel32" ( _
    ByVal lpBuffer As String, _
    ByVal uSize 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

GetSystemDirectoryA = ctypes.windll.kernel32.GetSystemDirectoryA
GetSystemDirectoryA.restype = wintypes.DWORD
GetSystemDirectoryA.argtypes = [
    wintypes.LPSTR,  # lpBuffer : LPSTR optional, out
    wintypes.DWORD,  # uSize : DWORD
]
# GetLastError: use ctypes.GetLastError() (or ctypes.WinDLL(use_last_error=True))

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('KERNEL32.dll')
GetSystemDirectoryA = Fiddle::Function.new(
  lib['GetSystemDirectoryA'],
  [
    Fiddle::TYPE_VOIDP,  # lpBuffer : LPSTR optional, out
    -Fiddle::TYPE_INT,  # uSize : DWORD
  ],
  -Fiddle::TYPE_INT)

#[link(name = "kernel32")]
extern "system" {
    fn GetSystemDirectoryA(
        lpBuffer: *mut u8,  // LPSTR optional, out
        uSize: u32  // DWORD
    ) -> u32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("KERNEL32.dll", CharSet = CharSet.Ansi, SetLastError = true)]
public static extern uint GetSystemDirectoryA([MarshalAs(UnmanagedType.LPStr)] System.Text.StringBuilder lpBuffer, uint uSize);
"@
$api = Add-Type -MemberDefinition $sig -Name 'KERNEL32_GetSystemDirectoryA' -Namespace Win32 -PassThru
# $api::GetSystemDirectoryA(lpBuffer, uSize)

#uselib "KERNEL32.dll"
#func global GetSystemDirectoryA "GetSystemDirectoryA" sptr, sptr
; GetSystemDirectoryA varptr(lpBuffer), uSize   ; 戻り値は stat
; lpBuffer : LPSTR optional, out -> "sptr"
; uSize : DWORD -> "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 "KERNEL32.dll"
#cfunc global GetSystemDirectoryA "GetSystemDirectoryA" var, int
; res = GetSystemDirectoryA(lpBuffer, uSize)
; lpBuffer : LPSTR optional, out -> "var"
; uSize : DWORD -> "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。

; DWORD GetSystemDirectoryA(LPSTR lpBuffer, DWORD uSize)
#uselib "KERNEL32.dll"
#cfunc global GetSystemDirectoryA "GetSystemDirectoryA" var, int
; res = GetSystemDirectoryA(lpBuffer, uSize)
; lpBuffer : LPSTR optional, out -> "var"
; uSize : DWORD -> "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 (
	kernel32 = windows.NewLazySystemDLL("KERNEL32.dll")
	procGetSystemDirectoryA = kernel32.NewProc("GetSystemDirectoryA")
)

// lpBuffer (LPSTR optional, out), uSize (DWORD)
r1, _, err := procGetSystemDirectoryA.Call(
	uintptr(lpBuffer),
	uintptr(uSize),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // DWORD

function GetSystemDirectoryA(
  lpBuffer: PAnsiChar;   // LPSTR optional, out
  uSize: DWORD   // DWORD
): DWORD; stdcall;
  external 'KERNEL32.dll' name 'GetSystemDirectoryA';

result := DllCall("KERNEL32\GetSystemDirectoryA"
    , "Ptr", lpBuffer   ; LPSTR optional, out
    , "UInt", uSize   ; DWORD
    , "UInt")   ; return: DWORD

●GetSystemDirectoryA(lpBuffer, uSize) = DLL("KERNEL32.dll", "dword GetSystemDirectoryA(char*, dword)")
# 呼び出し: GetSystemDirectoryA(lpBuffer, uSize)
# lpBuffer : LPSTR optional, out -> "char*"
# uSize : DWORD -> "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)。