CoInitialize

  • Article

This function initializes the COM library on the current thread and identifies the concurrency model as single-thread apartment (STA). Applications must initialize the COM library before they can call COM library functions other than CoGetMalloc and memory allocation functions.

New applications should call CoInitializeEx instead of CoInitialize.

HRESULT CoInitialize(
  LPVOID pvReserved 
);

Parameters

  • pvReserved
    [in] Reserved; must be NULL.

Return Values

This function supports the standard return values E_INVALIDARG, E_OUTOFMEMORY, and E_UNEXPECTED, as well as the following:

  • S_OK
    The COM library was initialized successfully on this thread.
  • S_FALSE
    The COM library is already initialized on this thread.
  • RPC_E_CHANGED_MODE
    A previous call to CoInitializeEx specified the concurrency model for this thread as multithread apartment (MTA).

Remarks

CoInitializeEx provides the same functionality as CoInitialize and also provides a parameter to explicitly specify the thread's concurrency model. CoInitialize calls CoInitializeEx and specifies the concurrency model as single-thread apartment. Applications developed today should call CoInitializeEx rather than CoInitialize.

You need to initialize the COM library on a thread before you call any of the library functions except CoGetMalloc, to get a pointer to the standard allocator, and the memory allocation functions.

Once the concurrency model for a thread is set, it cannot be changed. A call to CoInitialize on an apartment that was previously initialized as multithreaded will fail and return RPC_E_CHANGED_MODE.

Typically, the COM library is initialized on a thread only once. Subsequent calls to CoInitialize or CoInitializeEx on the same thread will succeed, as long as they do not attempt to change the concurrency model, but will return S_FALSE. To close the COM library gracefully, each successful call to CoInitialize or CoInitializeEx, including those that return S_FALSE, must be balanced by a corresponding call to CoUninitialize. However, the first thread in the application that calls CoInitialize(0) or CoInitializeEx(COINIT_APARTMENTTHREADED) must be the last thread to call CoUninitialize(). If the call sequence is not in this order, then subsequent calls to CoInitialize on the STA will fail and the application will not work.

Because there is no way to control the order in which in-process servers are loaded or unloaded, it is not safe to call CoInitialize, CoInitializeEx, or CoUninitialize from the DllMain function.

To determine whether the platform supports this function, see Determining Supported COM APIs.

Requirements

OS Versions: Windows CE 3.0 and later.
Header: Objbase.h.
Link Library: Ole32.lib.

Last updated on Wednesday, April 13, 2005

© 2005 Microsoft Corporation. All rights reserved.