; DLL creation example

format PE GUI 4.0 DLL
entry DllEntryPoint

include 'win32a.inc'

section '.text' code readable executable

proc DllEntryPoint hinstDLL,fdwReason,lpvReserved
mov eax,TRUE
ret
endp

; VOID ShowErrorMessage(HWND hWnd,DWORD dwError);

proc ShowErrorMessage hWnd,dwError
  local lpBuffer:DWORD
lea eax,[lpBuffer]
invoke FormatMessage,FORMAT_MESSAGE_ALLOCATE_BUFFER+FORMAT_MESSAGE_FROM_SYSTEM,0,[dwError],LANG_NEUTRAL,eax,0,0
invoke MessageBox,[hWnd],[lpBuffer],NULL,MB_ICONERROR+MB_OK
invoke LocalFree,[lpBuffer]
ret
endp

; VOID ShowLastError(HWND hWnd);

proc ShowLastError hWnd
invoke GetLastError
stdcall ShowErrorMessage,[hWnd],eax
ret
endp

section '.idata' import data readable writeable

  library kernel,'KERNEL32.DLL',\
  user,'USER32.DLL'

  import kernel,\
GetLastError,'GetLastError',\
SetLastError,'SetLastError',\
FormatMessage,'FormatMessageA',\
LocalFree,'LocalFree'

  import user,\
MessageBox,'MessageBoxA'

section '.edata' export data readable

  export 'ERRORMSG.DLL',\
ShowErrorMessage,'ShowErrorMessage',\
ShowLastError,'ShowLastError'

section '.reloc' fixups data discardable