SetDllDirectory

Adds a directory to the search path used to locate DLLs for the application.

BOOL WINAPI SetDllDirectory(   _In_opt_ LPCTSTR lpPathName );

Parameters

lpPathName [in, optional]

The directory to be added to the search path. If this parameter is an empty string (""), the call removes the current directory from the default DLL search order. If this parameter is NULL, the function restores the default search order.

Return value

If the function succeeds, the return value is nonzero.

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

Remarks

The SetDllDirectory function affects all subsequent calls to the LoadLibrary and LoadLibraryEx functions. It also effectively disables safe DLL search mode while the specified directory is in the search path.

After calling SetDllDirectory, the standard DLL search path is:

1. The directory from which the application loaded.
2. The directory specified by the lpPathName parameter.
3. The system directory. Use the GetSystemDirectory function to get the path of this directory. The name of this directory is System32.
4. The 16-bit system directory. There is no function that obtains the path of this directory, but it is searched. The name of this directory is System.
5. The Windows directory. Use the GetWindowsDirectory function to get the path of this directory.
6. The directories that are listed in the PATH environment variable.

Each time the SetDllDirectory function is called, it replaces the directory specified in the previous SetDllDirectory call. To specify more than one directory, use the AddDllDirectory function and call LoadLibraryEx with LOAD_LIBRARY_SEARCH_USER_DIRS.

To revert to the standard search path used by LoadLibrary and LoadLibraryEx, call SetDllDirectory with NULL. This also restores safe DLL search mode based on the SafeDllSearchMode registry value.

To compile an application that uses this function, define _WIN32_WINNT as 0x0502 or later. For more information, see Using the Windows Headers.

Requirements

Minimum supported client	Windows Vista, Windows XP with SP1 [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Header	Winbase.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll
Unicode and ANSI names	SetDllDirectoryW (Unicode) and SetDllDirectoryA (ANSI)

from : https://msdn.microsoft.com/en-us/library/ms686203(VS.85).aspx

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