C++ Set an object as default argument (which is a reference)

Question

I have been looking for a reply for this a lot, but I cannot find nothing. My compiler doesn't give me any error or warning, but maybe there could be any danger into doing this:

class Dog
{
   Dog(): x(0) {}
   int x;
};

If I have a simple class, creating a function in another class like this:

class PetHouse
{
    void addDog(Dog& animal = Dog())
    {
       // Anything...
    }
};

Is the addDog() declaration right? I have an argument which is a reference and it's default value is a Dog() object, instead an existing object.

Is there any danger?

Thanks for reading!

Is it in Visual Studio? – StoryTeller - Unslander Monica Oct 13 '18 at 11:00 — StoryTeller - Unslander Monica, Oct 13 '18 at 11:00
Yes, it is Visual Studio – Juan JuezSarmiento Oct 13 '18 at 15:26 — Juan JuezSarmiento, Oct 13 '18 at 15:26

score 1 · Accepted Answer · answered Oct 13 '18 at 11:00

1

No, it isn't. It should not even compile, because non-const lvalue references do not bind to temporaries like Dog().

As @StoryTeller hints, you are probably using MSVC without /permissive-.

answered Oct 13 '18 at 11:00

Acorn

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1

Thanks I'm reading about /za and /permissive- flags. First time I hear about them in the 7 years I have been coding! – Juan JuezSarmiento Oct 13 '18 at 16:09
1

@JuanJuezSarmiento You are welcome! :) MSVC has never been a "proper" C++ compiler; although lately (2017 onward) is way, way better than previous releases in that regard. Hopefully they will finish their efforts in the upcoming 2019 compiler and finally provide a conformant C++ compiler. – Acorn Oct 13 '18 at 16:27

C++ Set an object as default argument (which is a reference)

1 Answers1