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The GlobalLock function locks a global memory object and returns a pointer to the first byte of the objectís memory block. The memory block associated with a locked memory object cannot be moved or discarded. For memory objects allocated with the GMEM_MOVEABLE flag, the function increments the lock count associated with the memory object.

LPVOID GlobalLock(

    HGLOBAL hMem 

// address of the global memory object



Identifies the global memory object. This handle is returned by either the GlobalAlloc or GlobalReAlloc function.

Return Values

If the function succeeds, the return value is a pointer to the first byte of the memory block.

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


The internal data structures for each memory object include a lock count that is initially zero. For movable memory objects, GlobalLock increments the count by one, and the GlobalUnlock function decrements the count by one. For each call that a process makes to GlobalLock for an object, it must eventually call GlobalUnlock. Locked memory will not be moved or discarded, unless the memory object is reallocated by using the GlobalReAlloc function. The memory block of a locked memory object remains locked until its lock count is decremented to zero, at which time it can be moved or discarded.

Memory objects allocated with the GMEM_FIXED flag always have a lock count of zero. For these objects, the value of the returned pointer is equal to the value of the specified handle.

If the specified memory block has been discarded or if the memory block has a zero-byte size, this function returns NULL.

Discarded objects always have a lock count of zero.

See Also

GlobalAlloc, GlobalFlags, GlobalReAlloc, GlobalUnlock

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