.. meta::
   :description: It looks like you will get error 3E6 when you call write file with an address not aligned to DWORD.

Error 3e6 with WriteFile
========================
.. post:: 27, Jun, 2005
   :tags: Assembly language
   :category: Win32
   :author: me
   :nocomments:

It looks like you will get error 3E6 when you call write file with an
address not aligned to DWORD.

.. code-block::

   ;=====================================================================
   ; hello.asm - Example Assembler program
   ;
   ; Author: Sheng Jiang
   ; Course: COSC 2425
   ; Date: 5/23/05
   ;=====================================================================

   .386
   .MODEL flat, stdcall
   option casemap:none

   include windows.inc
   include kernel32.inc
   include masm32.inc

   includelib kernel32.lib
   includelib masm32.lib

   .DATA
   align 1
   placeholder byte ?
   Message BYTE  'Hello World!',0
   messegelen dword $-Message
   errorcode dword 0
   .CODE
   Hello   PROC
   int 3
   sub esp,messegelen
   mov ecx,messegelen
   mov edi,esp
   sub  esp , 8 ;//2 local var
   invoke GetStdHandle, STD_OUTPUT_HANDLE
   mov  [ebp-4] , eax ;
   mov  eax  ,ebp
   sub  eax  ,8
   mov  [ebp-8] , eax;
   copystringtostack:
   dec edi
   mov byte ptr [edi],'a'
   loop copystringtostack
   mov byte ptr [edi+12],0
   invoke WriteFile, [ebp-4], edi, messegelen, near ptr [ebp-8],0
   add esp,8
   add esp,messegelen
   invoke GetLastError
   mov  errorcode,eax
   invoke ExitProcess, 0
   Hello   ENDP
   END Hello

Update: Raymond Chen explained the reason in his blog https://devblogs.microsoft.com/oldnewthing/20250605-00/?p=111250, basically Windows SDK requires aligned pointers, except for those decorated with UNALIGNED.
E.g. 

.. code-block:: C++

   LWSTDAPI_(int) SHFormatDateTimeA(
        _In_ const FILETIME UNALIGNED * pft,
        _Inout_opt_ DWORD * pdwFlags,
        _Out_writes_(cchBuf) LPSTR pszBuf,
        UINT cchBuf);