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GlobalUnlock info  Overview  Group

The GlobalUnlock function decrements the lock count associated with a memory object that was allocated with the GMEM_MOVEABLE flag. This function has no effect on memory objects allocated with the GMEM_FIXED flag.

BOOL GlobalUnlock(

    HGLOBAL hMem 

// handle to the global memory object



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

Return Values

If the memory object is still locked after decrementing the lock count, the return value is a nonzero value.

If the function fails, the return value is zero. To get extended error information, call GetLastError. If GetLastError returns NO_ERROR, the memory object is unlocked.


The internal data structures for each memory object include a lock count that is initially zero. For movable memory objects, the GlobalLock function increments the count by one, and GlobalUnlock 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. If the specified memory block is fixed memory, this function returns TRUE.

If the memory object is already unlocked, GlobalUnlock returns FALSE and GetLastError reports ERROR_NOT_LOCKED. Memory objects allocated with the LMEM_FIXED flag always have a lock count of zero and cause the ERROR_NOT_LOCKED error.

A process should not rely on the return value to determine the number of times it must subsequently call GlobalUnlock for a memory object.

See Also

GlobalAlloc, GlobalFlags, GlobalLock, GlobalReAlloc

See also:

file: /Techref/os/win/api/win32/func/src/f44_7.htm, 3KB, , updated: 2008/2/21 06:44, local time: 2022/5/17 06:51,

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