HeapFree (Compact 2013)

3/28/2014

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

Syntax

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

Parameters

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

  If this parameter is set to NULL, the standard invalid parameter error code is returned. To get extended error information, call GetLastError.

• dwFlags
  [in] Controllable aspects of freeing a memory block. Only one flag is currently defined; however, all other flag values are reserved.

  Specifying HEAP_NO_SERIALIZE overrides the corresponding flag specified in the flOptions parameter when the heap was created using the HeapCreate function. This flag specifies that mutual exclusion is be used while HeapFree is accessing the heap.

  Do not specify this flag when accessing the process heap. The system might create additional threads within the application's process that simultaneously access the process heap.

  This flag is ignored.

• lpMem
  [in] Valid pointer to the memory block to be freed.

  This pointer is returned by the HeapAlloc or HeapReAlloc function.

Return Value

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, but it must be used when 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 is 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.

If NULL is passed as the hHeap parameter, the standard invalid parameter error code is returned. To get extended error information, call GetLastError.

Requirements

See Also

Reference

Memory Management Functions
GetProcessHeap
HeapAlloc
HeapCreate
HeapDestroy
HeapReAlloc
HeapSize