LocalLock function (winbase.h)

Article
10/13/2021

Locks a local memory object and returns a pointer to the first byte of the object's memory block.

Note The local 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 local function should be used. For more information, see Global and Local Functions.

Syntax

LPVOID LocalLock(
  [in] HLOCAL hMem
);

Parameters

[in] hMem

A handle to the local memory object. This handle is returned by either the LocalAlloc or LocalReAlloc function.

Return value

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.

Remarks

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

Memory objects allocated with LMEM_FIXED 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.

Requirements

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