Undefined reference to error is showing an extra parameter for my function, GTKMM C++

Question

I am writing a snakes and ladders game and I defined a function called draw_snake as follows:

void draw_snake(const Cairo::RefPtr<Cairo::Context>& cr, 
                std::pair<int,int> snake, 
                std::vector< std::pair<int,int> > boardcoords);

When I make the call to this function I do it as follows:

pair<int, int> snake = make_pair(100,1);
draw_snake(cr, snake, boardcoords);

boardcoords is a vector of pair<int,int>. The error message is saying that I have a fourth parameter when i call the function. The error message is this:

myarea.cc:(.text+0x7db): undefined reference to `MyArea::draw_snake(Cairo::RefPtr<Cairo::Context> const&, std::pair<int, int>, std::vector<std::pair<int, int>, std::allocator<std::pair<int, int> > >)'

Where is it getting this allocator from?

Answer 1

You're misreading the error. The function has three parameters.

undefined reference to `MyArea::draw_snake(
         Cairo::RefPtr<Cairo::Context> const&,
         std::pair<int, int>,
         std::vector<std::pair<int, int>, std::allocator<std::pair<int, int> > >
//                  ^ The vector's parameters are contained in these brackets  ^
         )

std::vector has a default "allocator" parameter. It exists even when you don't specify it.

So the error you're getting is that the exact function you declared is not defined.