GlobalReAlloc function (winbase.h)

Article
10/13/2021

Changes the size or attributes of a specified global memory object. The size can increase or decrease.

Note The global functions have greater overhead and provide fewer features than other memory management functions. New applications should use the heap functions unless documentation states that a global function should be used. For more information, see Global and Local Functions.

Syntax

DECLSPEC_ALLOCATOR HGLOBAL GlobalReAlloc(
  [in] _Frees_ptr_ HGLOBAL hMem,
  [in] SIZE_T              dwBytes,
  [in] UINT                uFlags
);

Parameters

[in] hMem

A handle to the global memory object to be reallocated. This handle is returned by either the GlobalAlloc or GlobalReAlloc function.

[in] dwBytes

The new size of the memory block, in bytes. If uFlags specifies GMEM_MODIFY, this parameter is ignored.

[in] uFlags

The reallocation options. If GMEM_MODIFY is specified, the function modifies the attributes of the memory object only (the dwBytes parameter is ignored.) Otherwise, the function reallocates the memory object.

You can optionally combine GMEM_MODIFY with the following value.

Value	Meaning
GMEM_MOVEABLE 0x0002	Allocates movable memory. If the memory is a locked GMEM_MOVEABLE memory block or a GMEM_FIXED memory block and this flag is not specified, the memory can only be reallocated in place.

If this parameter does not specify GMEM_MODIFY, you can use the following value.

Value	Meaning
GMEM_ZEROINIT 0x0040	Causes the additional memory contents to be initialized to zero if the memory object is growing in size.

Return value

If the function succeeds, the return value is a handle to the reallocated memory object.

If the function fails, the return value is NULL. To get extended error information, call GetLastError.

Remarks

If GlobalReAlloc reallocates a movable object, the return value is a handle to the memory object. To convert the handle to a pointer, use the GlobalLock function.

If GlobalReAlloc reallocates a fixed object, the value of the handle returned is the address of the first byte of the memory block. To access the memory, a process can simply cast the return value to a pointer.

If GlobalReAlloc fails, the original memory is not freed, and the original handle and pointer are still valid.

Requirements

Requirement	Value
Minimum supported client	Windows XP [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2003 [desktop apps \| UWP apps]
Target Platform	Windows
Header	winbase.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll