Copy constructor called on singleton class

Question

I have the following problem. I have a singleton with a getInstance member function that returns an instance. I call this somewhere in code and for some reason VC tries to call the copy constructor. Why is this? How do I fix this?

The header:

class FileSystemEntryCollection {
public:
    static FileSystemEntryCollection &getInstance();
private:
    FileSystemEntryCollection();
    FileSystemEntryCollection(FileSystemEntryCollection const&);
    void operator=(FileSystemEntryCollection const&);
}

Source file:

FileSystemEntryCollection &FileSystemEntryCollection::getInstance() {
    static FileSystemEntryCollection instance = FileSystemEntryCollection();
    return instance;
}

The following line calls the copy constructor:

auto collection = FileSystemEntryCollection::getInstance();

I've tried to leave in the relevant code, let me know if something else is needed.

Answer 1

auto collection = FileSystemEntryCollection::getInstance();

needs to be:

auto& collection = FileSystemEntryCollection::getInstance();
    ^

auto on its own is never a reference type.

Answer 2

With a different compiler you'll get the same error for the initialization of instance.

static FileSystemEntryCollection instance = FileSystemEntryCollection();

The = here calls for copy construction: formally, the compiler creates a temporary (FileSystemEntryCollection()), and copies that into instance. However, in this situation, compilers are allowed to skip the copy construction and construct the object directly in place. That's what your compiler is doing. But compilers aren't required to do this.

Better:

static FileSystemEntryCollection instance;

which uses the default constructor to create instance.