title _unlock | Microsoft Docs ms.custom ms.date 11/04/2016 ms.reviewer ms.suite ms.technology cpp-standard-libraries ms.tgt_pltfrm ms.topic article apiname _unlock apilocation msvcrt.dll msvcr100.dll msvcr110_clr0400.dll msvcr110.dll msvcr80.dll msvcr120.dll msvcr90.dll msvcr120_clr0400.dll apitype DLLExport f1_keywords unlock _unlock dev_langs C++ helpviewer_keywords unlock function _unlock function ms.assetid 2eda2507-a134-4997-aa12-f2f8cb319e14 caps.latest.revision 5 author corob-msft ms.author corob manager ghogen ms.workload cplusplus _unlock Releases a multi-thread lock. ImportantThis function is obsolete. Beginning in Visual Studio 2015, it is not available in the CRT. Syntax void __cdecl _unlock( int locknum ); Parameters [in] locknum The identifier of the lock to release. Requirements Source: mlock.c See Also Alphabetical Function Reference _lock