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HeapFree

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This function frees a memory block allocated from a heap by the HeapAlloc or HeapReAlloc function.

BOOL HeapFree(
  HANDLE hHeap, 
  DWORD dwFlags, 
  LPVOID lpMem 
);

Parameters

  • hHeap
    [in] Handle to the heap whose memory block is freed by the function. This parameter is a handle returned by the HeapCreate or GetProcessHeap function.

  • dwFlags
    [in] Specifies several controllable aspects of freeing a memory block. Only one flag is currently defined; however, all other flag values are reserved for future use. The following table shows the flag you can specify. Specifying this flag will override the corresponding flag specified in the flOptions parameter when the heap was created using the HeapCreate function.

    Value Description
    HEAP_NO_SERIALIZE Specifies that mutual exclusion will not be used while HeapFree is accessing the heap. This flag should not be specified when accessing the process heap. The system may create additional threads within the application's process that simultaneously access the process heap.

    This flag is ignored.

  • lpMem
    [in] Pointer to the memory block to be freed. This pointer is returned by the HeapAlloc or HeapReAlloc function.

Return Values

Nonzero indicates success. Zero indicates failure. To get extended error information, call GetLastError.

Remarks

Serialization ensures mutual exclusion when two or more threads attempt to simultaneously allocate or free blocks from the same heap. There is a small performance cost to serialization, but it must be used whenever multiple threads allocate and free memory from the same heap. A critical section is always used to serialize access to an individual heap. There is a critical section per heap to protect access to each heap. An attempt to grab a critical section that is not owned is a fast path operation that incurs little overhead. This would be similar to using the HEAP_NO_SERIALIZE flag if only one thread was ever accessing a particular heap. If there is contention for the critical section and therefore the heap, a new thread request to allocate heap space will serialize.

Requirements

OS Versions: Windows CE 1.0 and later.
Header: Winbase.h.
Link Library: Coredll.lib.

See Also

GetProcessHeap | HeapAlloc | HeapCreate | HeapDestroy | HeapReAlloc | HeapSize

Last updated on Wednesday, April 13, 2005

© 2005 Microsoft Corporation. All rights reserved.