CODEWITHSUNDEEP
c++pointersint
TooMuchCoffee
TooMuchCoffee

Reputation: 31

C/C++ - Integers clashing with pointers

I've been working on a small library collection, and in my n-dimensional geometric vector template class, I've run into an issue between two constructors. The constructor VectorN( t data[n] ) clashes with constructor VectorN( t value ), and I get the error:

More than one instance of constructor ___ matches the argument list".

I understand why this is occuring, but a solution eludes me. The issue only occurs when I attempt to instantiate the class using VectorN(0), but when value is anything other than 0 the correct constructor is used. What can I do to fix this?

Upvotes: 0

Views: 130

Answers (3)

Slava
Slava

Reputation: 44238

You improperly declared constructor that accepts C style array - you are loosing size. If you do that correctly:

template <class T>
class VectorN {
public:
    template<std::size_t N>
    VectorN( T (&array)[N] );
    ...
};

then problem with 0 would disappear.

Upvotes: 3

PeterO
PeterO

Reputation: 480

If you pass an array like t data[n], actually you just pass a pointer on the first element of the array. So your first constructor is equal to VectorN(t* data). So now when you call the constructor with zero, the compiler might as well think you want to pass the null-pointer.

I would recommend you to clearly distinguish your constructors. So for example since you have a n-dimensional vector, you have to specify the n somewhere. You could do a constructor like: VectorN(t* data, int n). Than it is definitely clear where you want to use what constructor.

Upvotes: 0

Puppy
Puppy

Reputation: 146910

The problem is that 0 is a valid null pointer constant, which is a valid T* (which is what t data[n] actually is under the hood). If you really want to take raw C arrays, use a reference to the array- this is strongly typed and safe(r).

Also, raw C arrays are shit. std::array is for when you want to not segfault.

Upvotes: 5

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