Wow64EnableWow64FsRedirection function (wow64apiset.h)

Article
04/13/2022

Enables or disables file system redirection for the calling thread.

This function may not work reliably when there are nested calls. Therefore, this function has been replaced by the Wow64DisableWow64FsRedirection and Wow64RevertWow64FsRedirection functions.

Note These two methods of controlling file system redirection cannot be combined in any way. Do not use the Wow64EnableWow64FsRedirection function with either the Wow64DisableWow64FsRedirection or the Wow64RevertWow64FsRedirection function.

Syntax

BOOLEAN Wow64EnableWow64FsRedirection(
  BOOLEAN Wow64FsEnableRedirection
);

Parameters

Wow64FsEnableRedirection

Indicates the type of request for WOW64 system folder redirection. If TRUE, requests redirection be enabled; if FALSE, requests redirection be disabled.

Return value

Boolean value indicating whether the function succeeded. If TRUE, the function succeeded; if FALSE, the function failed.

Remarks

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.

Note The Wow64EnableWow64FsRedirection function affects all file operations performed by the current thread, which can have unintended consequences if file system redirection is disabled for any length of time. For example, DLL loading depends on file system redirection, so disabling file system redirection will cause DLL loading to fail. Also, many feature implementations use delayed loading and will fail while redirection is disabled. The failure state of the initial delay-load operation is persisted, so any subsequent use of the delay-load function will fail even after file system redirection is re-enabled. To avoid these problems, disable file system redirection immediately before calls to specific file I/O functions (such as CreateFile) that must not be redirected, and re-enable file system redirection immediately afterward using Wow64EnableWow64FsRedirection(TRUE).

File redirection is enabled or disabled only for the thread calling this function. This affects only operations made by the current thread. Some functions, such as CreateProcessAsUser, do their work on another thread, which is not affected by the state of file system redirection in the calling thread.

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

Technology	Supported
Server Message Block (SMB) 3.0 protocol	No
SMB 3.0 Transparent Failover (TFO)	No
SMB 3.0 with Scale-out File Shares (SO)	No
Cluster Shared Volume File System (CsvFS)	Yes
Resilient File System (ReFS)	No

Examples

#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;

  //  Disable redirection immediately prior to the native API
  //  function call.
  if( Wow64EnableWow64FsRedirection(FALSE) ) 
   {
    //  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 == Wow64EnableWow64FsRedirection(TRUE) )
     {
      //  Failure to re-enable redirection should be considered
      //  a critical failure and execution aborted.
      return;
     }
   }
    
  // The handle, if valid, can be used as usual without
  // leaving redirection disabled.
 
  if( INVALID_HANDLE_VALUE != hFile )  
   {
    // Use the file handle
   }
 }

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Target Platform	Windows
Header	wow64apiset.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll

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