IUnknown_AtomicRelease function (shlwapi.h)

Article
02/22/2024

Releases a Component Object Model (COM) pointer and sets it to NULL.

Syntax

void IUnknown_AtomicRelease(
  [in, out, optional] void **ppunk
);

Parameters

[in, out, optional] ppunk

Type: void**

The address of a pointer to a COM interface.

Return value

None

Remarks

If ppunk points to a NULL pointer, no operation is performed. Otherwise, ppunk is assumed to be the address of a COM interface pointer, derived from IUnknown. The function calls the interface's IUnknown::Release method then sets the interface pointer to NULL.

Examples

The following example uses IUnknown_AtomicRelease to release the stream, if it exists. If not, it does nothing.

void sample()
{
    IStream *pstm = NULL;
    CreateStreamOnHGlobal(NULL, TRUE, &pstm);
    
    IUnknown_AtomicRelease((void**)&pstm);
    
    // At this point, pstm is NULL
}

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional, Windows XP [desktop apps only]
Minimum supported server	Windows 2000 Server, Windows Server 2003 [desktop apps only]
Target Platform	Windows
Header	shlwapi.h
DLL	Shlwapi.dll (version 5.0 or later)

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