Code shared from run.dlang.io.

main.d

void main()
{
    import std.experimental.allocator;
    import std.experimental.allocator.mallocator: Mallocator;
    import std.experimental.allocator.gc_allocator : GCAllocator;
    auto newAlloc = sharedAllocatorObject(Mallocator.instance);
    processAllocator() = newAlloc;
    assert(processAllocator is newAlloc);
    processAllocator = sharedAllocatorObject(GCAllocator.instance);
}