function reallocates a block of memory from a heap. This function enables you
to resize a memory block and change other memory block properties. The
allocated memory is not movable.
| HANDLE hHeap,
||// handle to a heap block
| DWORD dwFlags,
||// heap reallocation flags
| LPVOID lpMem,
||// pointer to the memory to reallocate
| DWORD dwBytes
||// number of bytes to reallocate
Specifies the heap from which the memory will be reallocated. This is a handle
returned by the HeapCreate
Specifies several controllable aspects of heap reallocation. Specifying any of
these flags will override 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:
||Specifies that the operating-system will raise an exception to indicate a
function failure, such as an out-of-memory condition, instead of returning NULL.
||Specifies that mutual exclusion will not be used while this function is
accessing the heap. For more information about HEAP_NO_SERIALIZE, see the Remarks
section of HeapCreate.
||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 will
fail, leaving the original memory block unchanged.
||If the reallocation request is for a larger size, this flag specifies that the
additional region of memory beyond the original size will be initialized to
zero. The contents of the memory block up to its original size are unaffected.
Points to the block of memory that the function reallocates. This pointer is
returned by an earlier call to the HeapAlloc
Specifies the new size of the memory block, in bytes. A memory block's size
can be increased or decreased by using this function.
If the heap specified by the hHeap
parameter is a "non-growable" heap, dwBytes
must be less than 0x7FFF8. You create a non-growable heap by calling the HeapCreate
function with a nonzero value.
If the function succeeds, the return value is a pointer to the reallocated
If the function fails and you have not specified HEAP_GENERATE_EXCEPTIONS, the
return value is NULL.
If the function fails and you have specified HEAP_GENERATE_EXCEPTIONS, the
function may generate the following exceptions:
||The reallocation attempt failed for lack of available memory.
||The reallocation attempt failed because of heap corruption or improper
If the function fails, it calls SetLastError
. An application can call GetLastError
for extended error information.
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
To free a block of memory allocated by HeapReAlloc
, use the HeapFree
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