Function dealloc 

pub unsafe fn dealloc(
    system_table: *mut SystemTable,
    ptr: *mut u8,
    layout: Layout,
)

Deallocate Memory from UEFI Boot-Services

Use the UEFI free_pool boot-services to release a block of memory previously allocated through alloc().

Safety

The memory block must be the same as previously returned by alloc(). Furthermore, this function must be able to call the UEFI boot-servies through the specified system table, and this must match the same boot-services the memory block was allocated through.

The passed layout must match the layout used to allocate the memory block.