i use SharedMemory with x64,
while i set size > 4G , then error,
std::size_t size = 1024LL * 1024 * 1024 * 4;
SharedMemory mem("MySharedMemory", size, SharedMemory::AM_WRITE);

and i find the define of _size is DWORD, while size_t is
#ifdef _WIN64
typedef unsigned __int64 size_t;
....
and _size(static_cast(size)) may lose high