Loads the specified module into the address space of the calling process. The specified module may cause other modules to be loaded.

For additional load options, use the LoadLibraryEx function.

Syntax

HMODULE WINAPI LoadLibrary(
  __in  LPCTSTR lpFileName
);

Parameters

lpFileName [in]

The name of the module. This can be either a library module (a .dll file) or an executable module (an .exe file). The name specified is the file name of the module and is not related to the name stored in the library module itself, as specified by the LIBRARY keyword in the module-definition (.def) file.

If the string specifies a path but the file does not exist in the specified directory, the function fails. When specifying a path, be sure to use backslashes (\), not forward slashes (/).

If the string does not specify a path, the function uses a standard search strategy to find the file. See the Remarks for more information.

Return Value

If the function succeeds, the return value is a handle to the module.

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

Remarks

To enable or disable error messages displayed by the loader during DLL loads, use the SetErrorMode function.

LoadLibrary can be used to load a library module into the address space of the process and return a handle that can be used in GetProcAddress to get the address of a DLL function. LoadLibrary can also be used to load other executable modules. For example, the function can specify an .exe file to get a handle that can be used in FindResource or LoadResource. However, do not use LoadLibrary to run an .exe file. Instead, use the CreateProcess function.

If the specified module is a DLL that is not already loaded for the calling process, the system calls the DLL's DllMain function with the DLL_PROCESS_ATTACH value. If DllMain returns TRUE, LoadLibrary returns a handle to the module. If DllMain returns FALSE, the system unloads the DLL from the process address space and LoadLibrary returns NULL. It is not safe to call LoadLibrary from DllMain. For more information, see the Remarks section in DllMain.

Module handles are not global or inheritable. A call to LoadLibrary by one process does not produce a handle that another process can use — for example, in calling GetProcAddress. The other process must make its own call to LoadLibrary for the module before calling GetProcAddress.

If lpFileName does not include a path and there is more than one loaded module with the same base name and extension, the function returns a handle to the module that was loaded first.

If no file name extension is specified in the lpFileName parameter, the default library extension .dll is appended. However, the file name string can include a trailing point character (.) to indicate that the module name has no extension. When no path is specified, the function searches for loaded modules whose base name matches the base name of the module to be loaded. If the name matches, the load succeeds. Otherwise, the function searches for the file. For more information on the DLL search order, see Dynamic-Link Library Search Order.

The first directory searched is the directory containing the image file used to create the calling process (for more information, see the CreateProcess function). Doing this allows private dynamic-link library (DLL) files associated with a process to be found without adding the process's installed directory to the PATH environment variable.

The search path can be altered using the SetDllDirectory function. This solution is recommended instead of using SetCurrentDirectory or hard-coding the full path to the DLL.

If a path is specified and there is a redirection file for the application, the function searches for the module in the application's directory. If the module exists in the application's directory, LoadLibrary ignores the specified path and loads the module from the application's directory. If the module does not exist in the application's directory, LoadLibrary loads the module from the specified directory. For more information, see Dynamic Link Library Redirection.

If you call LoadLibrary with the name of an assembly without a path specification and the assembly is listed in the system compatible manifest, the call is automatically redirected to the side-by-side assembly.

The system maintains a per-process reference count on all loaded modules. Calling LoadLibrary increments the reference count. Calling the FreeLibrary or FreeLibraryAndExitThread function decrements the reference count. The system unloads a module when its reference count reaches zero or when the process terminates (regardless of the reference count).

Windows Server 2003 and Windows XP:  The Visual C++ compiler supports a syntax that enables you to declare thread-local variables: _declspec(thread). If you use this syntax in a DLL, you will not be able to load the DLL explicitly using LoadLibrary on versions of Windows prior to Windows Vista. If your DLL will be loaded explicitly, you must use the thread local storage functions instead of _declspec(thread). For an example, see Using Thread Local Storage in a Dynamic Link Library.

Examples

For an example, see Using Run-Time Dynamic Linking.

Requirements

See Also

DllMain
Dynamic-Link Library Functions
FindResource
FreeLibrary
GetProcAddress
GetSystemDirectory
GetWindowsDirectory
LoadLibraryEx
LoadResource
Run-Time Dynamic Linking
SetDllDirectory
SetErrorMode

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Build date: 8/7/2008