Wow64DisableWow64FsRedirection function (wow64apiset.h)

Disables file system redirection for the calling thread. File system redirection is enabled by default.

BOOL Wow64DisableWow64FsRedirection(
  [out] PVOID *OldValue
);

[out] OldValue

The WOW64 file system redirection value. The system uses this parameter to store information necessary to revert (re-enable) file system redirection.

If the function succeeds, the return value is a nonzero value.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

This function is useful for 32-bit applications that want to gain access to the native system32 directory. By default, WOW64 file system redirection is enabled.

The Wow64DisableWow64FsRedirection/Wow64RevertWow64FsRedirection function pairing is a replacement for the functionality of the Wow64EnableWow64FsRedirection function.

To restore file system redirection, call the Wow64RevertWow64FsRedirection function. Every successful call to the Wow64DisableWow64FsRedirection function must have a matching call to the Wow64RevertWow64FsRedirection function. This will ensure redirection is re-enabled and frees associated system resources.

In Windows 8 and Windows Server 2012, this function is supported by the following technologies.

The following example uses Wow64DisableWow64FsRedirection to disable file system redirection so that a 32-bit application that is running under WOW64 can open the 64-bit version of Notepad.exe in %SystemRoot%\System32 instead of being redirected to the 32-bit version in %SystemRoot%\SysWOW64.

#ifdef _WIN32_WINNT
#undef _WIN32_WINNT
#endif
#define _WIN32_WINNT 0x0501

#ifdef NTDDI_VERSION
#undef NTDDI_VERSION
#endif
#define NTDDI_VERSION 0x05010000

#include <Windows.h>

void main()
{
    HANDLE hFile = INVALID_HANDLE_VALUE;
    PVOID OldValue = NULL;

    //  Disable redirection immediately prior to the native API
    //  function call.
    if( Wow64DisableWow64FsRedirection(&OldValue) ) 
    {
        //  Any function calls in this block of code should be as concise
        //  and as simple as possible to avoid unintended results.
        hFile = CreateFile(TEXT("C:\\Windows\\System32\\Notepad.exe"),
            GENERIC_READ,
            FILE_SHARE_READ,
            NULL,
            OPEN_EXISTING,
            FILE_ATTRIBUTE_NORMAL,
            NULL);

        //  Immediately re-enable redirection. Note that any resources
        //  associated with OldValue are cleaned up by this call.
        if ( FALSE == Wow64RevertWow64FsRedirection(OldValue) )
        {
            //  Failure to re-enable redirection should be considered
            //  a critical failure and execution aborted.
            return;
        }
    }
    
    //  The handle, if valid, now can be used as usual, and without
    //  leaving redirection disabled. 
    if( INVALID_HANDLE_VALUE != hFile )  
    {
        // Use the file handle
    }
}

File Management Functions

File System Redirector

Wow64EnableWow64FsRedirection

Wow64RevertWow64FsRedirection