This function reallocates a block of memory from a heap. The allocated memory is not movable.
At a Glance
| Header file: | Winbase.h |
| Windows CE versions: | 1.0 and later |
Syntax
LPVOID HeapReAlloc(HANDLE hHeap, DWORD dwFlags,
LPVOID lpMem, DWORD dwBytes);
Parameters
hHeap
[in] Heap from which the memory will be reallocated. This is a handle returned by the HeapCreate or GetProcessHeap function.
dwFlags
[in] Specifies several controllable aspects of heap reallocation. Specifying any of these flags overrides the corresponding flag specified in the flOptions parameter when the heap was created by using the HeapCreate function. You can specify one or more of the following flags:
| Value | Description |
| HEAP_NO_SERIALIZE | Specifies that mutual exclusion is not used while HeapReAlloc 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. | |
| HEAP_REALLOC_IN_PLACE_ONLY | Specifies that there can be no movement when reallocating a memory block to a larger size. If this flag is not specified and the reallocation request is for a larger size, the function may move the block to a new location. If this flag is specified and the block cannot be enlarged without moving, the function fails, leaving the original memory block unchanged. |
| HEAP_ZERO_MEMORY | If the reallocation request is for a larger size, this flag specifies that the additional region of memory beyond the original size be initialized to zero. The contents of the memory block up to its original size are unaffected. |
lpMem
[in] Pointer to the block of memory that the function reallocates. This pointer is returned by an earlier call to the HeapAlloc or HeapReAlloc function.
dwBytes
[in] Specifies the new size of the memory block, in bytes. A memory block’s size can be increased or decreased by using this function.
Return Values
If the function fails, it calls SetLastError. An application can call GetLastError for extended error information.
Remarks
If HeapReAlloc succeeds, it allocates at least the amount of memory requested. If the actual amount allocated is greater than the amount requested, the process can use the entire amount. To determine the actual size of the reallocated block, use the HeapSize function.
If HeapReAlloc fails, the original memory is not freed, and the original handle and pointer are still valid.
To free a block of memory allocated by HeapReAlloc, use the HeapFree function.
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. Setting the HEAP_NO_SERIALIZE flag eliminates mutual exclusion on the heap. Without serialization, two or more threads that use the same heap handle might attempt to allocate or free memory simultaneously, likely causing corruption in the heap. The HEAP_NO_SERIALIZE flag can, therefore, be safely used only in the following situations:
See Also