Can't assign 2D-array of function pointers

Question

I have "This declaration has no storage class or type specifier" error in Visual Studio than I try to initialize my array with functions. I'm declare an array in header:

typedef void (*MultimethodFunc)(ofstream& out);

extern MultimethodFunc multimethodFunc[][10];

In .cpp file I have this:

MultimethodFunc multimethodFunc[10][10];

And finally I try to initialize it in another .cpp:

void TrainTrainOut(ofstream& out) {
    out << "\nTrain and Train" << endl;
}

void MMTrainTrainOut(ofstream& out) {
    return TrainTrainOut(out);
}

multimethodFunc[1][1] = MMTrainTrainOut;
multimethodFunc[1][2] = MMTrainAirplaneOut;
multimethodFunc[2][1] = MMAirplaneTrainOut;
multimethodFunc[2][2] = MMAirplaneAirplaneOut;

Another functions just similar to TrainTrainOut and MMTrainTrainOut with different outs and matching returns. The error is placed in last strings there I try to assign functions to arrray. What I'm doing wrong in this case? Thank you!

Those aren't initializations those are assignments. MultimethodFunc muntimethodFunc[10][10] = { /* values here */ }; that would be an initialization. — Wyck
– Wyck, Commented Jan 8, 2020 at 4:55
You can't put an assignment at file scope. Put the assignments in a function and call the function. — Wyck
– Wyck, Commented Jan 8, 2020 at 4:59
@Wyck, how can I do that? Just make another function and place assignments in it? — D3mark0
– D3mark0, Commented Jan 8, 2020 at 5:03

Wyck · Accepted Answer · 2020-01-08 05:07:00Z

You can't put an assignment at file scope.

The following program gives the error:

this declaration has no storage class or type specifier

#include <fstream>

using namespace std;

typedef void (*MultimethodFunc)(ofstream& out);

void TrainTrainOut(ofstream& out) {
    out << "\nTrain and Train" << endl;
}

void MMTrainTrainOut(ofstream& out) {
    return TrainTrainOut(out);
}

MultimethodFunc multimethodFunc[10][10];

multimethodFunc[1][1] = MMTrainTrainOut;  /* ERROR HERE */
multimethodFunc[1][2] = MMTrainTrainOut;
multimethodFunc[2][1] = MMTrainTrainOut;
multimethodFunc[2][2] = MMTrainTrainOut;

int main() {

}

The following program compiles. It fixes the problem by moving the assignments into an initialization function and calling the initialization function explicitly somewhere (e.g.: main)

#include <fstream>

using namespace std;

typedef void (*MultimethodFunc)(ofstream& out);

void TrainTrainOut(ofstream& out) {
    out << "\nTrain and Train" << endl;
}

void MMTrainTrainOut(ofstream& out) {
    return TrainTrainOut(out);
}

MultimethodFunc multimethodFunc[10][10];


void initializeThings() {
    multimethodFunc[1][1] = MMTrainTrainOut;
    multimethodFunc[1][2] = MMTrainTrainOut;
    multimethodFunc[2][1] = MMTrainTrainOut;
    multimethodFunc[2][2] = MMTrainTrainOut;
}

int main() {
    initializeThings();
}

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