InitOnceInitialize function (synchapi.h)

Initializes a one-time initialization structure.


void InitOnceInitialize(
  [out] PINIT_ONCE InitOnce


[out] InitOnce

A pointer to the one-time initialization structure.

Return value



The InitOnceInitialize function is used to initialize a one-time initialization structure dynamically. To initialize the structure statically, assign the constant INIT_ONCE_STATIC_INIT to the structure variable.

To compile an application that uses this function, define _WIN32_WINNT as 0x0600 or later. For more information, see Using the Windows Headers.

A one-time initialization object cannot be moved or copied. The process must not modify the initialization object, and must instead treat it as logically opaque. Only use the one-time initialization functions to manage one-time initialization objects.


The following example calls InitOnceInitialize to initialize the one-time initialization structure named InitOnce. Alternatively, the structure can be declared as a global variable as shown in Using One-Time Initialization.

//Requires Windows Vista, Windows Server 2008 or later
#define _WIN32_WINNT 0x0600

#include <windows.h>

BOOL StartInitialization()
    INIT_ONCE InitOnce;


    return TRUE;


Requirement Value
Minimum supported client Windows Vista [desktop apps | UWP apps]
Minimum supported server Windows Server 2008 [desktop apps | UWP apps]
Target Platform Windows
Header synchapi.h (include Windows.h on Windows 7, Windows Server 2008 Windows Server 2008 R2)
Library Kernel32.lib
DLL Kernel32.dll

See also


One-Time Initialization

Synchronization Functions