FreeLibrary function

Frees the loaded dynamic-link library (DLL) module and, if necessary, decrements its reference count. When the reference count reaches zero, the module is unloaded from the address space of the calling process and the handle is no longer valid.

Syntax

BOOL FreeLibrary(
  HMODULE hLibModule
);

Parameters

hLibModule

A handle to the loaded library module. The LoadLibrary, LoadLibraryEx,
GetModuleHandle, or GetModuleHandleEx function returns this handle.

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 the GetLastError function.

Remarks

The system maintains a per-process reference count for each loaded module. A module that was loaded at process initialization due to load-time dynamic linking has a reference count of one. The reference count for a module is incremented each time the module is loaded by a call to LoadLibrary. The reference count is also incremented by a call to LoadLibraryEx unless the module is being loaded for the first time and is being loaded as a data or image file.

The reference count is decremented each time the FreeLibrary or FreeLibraryAndExitThread function is called for the module. When a module's reference count reaches zero or the process terminates, the system unloads the module from the address space of the process. Before unloading a library module, the system enables the module to detach from the process by calling the module's DllMain function, if it has one, with the DLL_PROCESS_DETACH value. Doing so gives the library module an opportunity to clean up resources allocated on behalf of the current process. After the entry-point function returns, the library module is removed from the address space of the current process.

It is not safe to call FreeLibrary from DllMain. For more information, see the Remarks section in DllMain.

Calling FreeLibrary does not affect other processes that are using the same module.

Use caution when calling FreeLibrary with a handle returned by GetModuleHandle. The GetModuleHandle function does not increment a module's reference count, so passing this handle to FreeLibrary can cause a module to be unloaded prematurely.

A thread that must unload the DLL in which it is executing and then terminate itself should call FreeLibraryAndExitThread instead of calling FreeLibrary and ExitThread separately. Otherwise, a race condition can occur. For details, see the Remarks section of FreeLibraryAndExitThread.

Examples

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

Requirements

   
Minimum supported client Windows XP [desktop apps | UWP apps]
Minimum supported server Windows Server 2003 [desktop apps | UWP apps]
Target Platform Windows
Header libloaderapi.h (include Windows.h)
Library Kernel32.lib
DLL Kernel32.dll

See Also

DllMain

Dynamic-Link Library Functions

FreeLibraryAndExitThread

GetModuleHandle

GetModuleHandleEx

LoadLibrary

Run-Time Dynamic Linking