Dynamic object creation of an array of pointers

Question

I try to create objects dynamically. Each object is a pointer in an array of pointers. The compiler gives me

error C4700: uninitialized local variable 'villages' used.

And I can not figure out how to fix it. I would be very grateful to all the helpers.

    int villageAmount;
    cout << "Defining villages:\n\nEnter how many villages do you want: ";
    cin >> villageAmount;
    Village **villages;
    for (int i = 0; i < villageAmount; i++)
    {
        cout << "\nDefining village's details #" << i + 1 << ":\n";
        villages[i] = new (nothrow) Village;
    }

Is this what you want to do? villages = new Village*[villageAmount] ? — MFisherKDX
– MFisherKDX, Commented Mar 15, 2019 at 0:18
villages is never assigned storage, so villages[i] points Crom-knows where. It needs something like villages = new Village *[villageAmount]; But instead save youeself a LOT of pain and suffering and read up on std::vector — user4581301
– user4581301, Commented Mar 15, 2019 at 0:19
@user4581301 -- who is Crom? Never heard that one before. <g> — MFisherKDX
– MFisherKDX, Commented Mar 15, 2019 at 0:19
Recommended reading: Why should C++ programmers minimize use of 'new'? — user4581301
– user4581301, Commented Mar 15, 2019 at 0:19
What about std::vector<> and why do you need pointers? Can't you just use normal objects and place them in the container? — Loki Astari
– Loki Astari, Commented Mar 15, 2019 at 0:32

xvnm · Accepted Answer · 2019-03-15 00:25:56Z

3

Village **villages;

you declared villages without initializing, so it contains garabage valaue.

for (int i = 0; i < villageAmount; i++)
{
    cout << "\nDefining village's details #" << i + 1 << ":\n";
    villages[i] = new (nothrow) Village;
}

right below, you access into it and writes. That's no no.

If you want to store pointer of village (i.e. type of Village*) dynamically, you also need to allocate them.

Village **villages = new Village*[villageAmount];

Or if amount is fixed,

Village *villages[10] = { nullptr, }; // 10, 12344, or whatever

answered Mar 15, 2019 at 0:25

xvnm

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Comments

Guillaume Magniadas · Accepted Answer · 2019-03-15 00:45:08Z

1

villages memory is never allocated, you should use a vector or any sort of container (an array look fine here). If you really want to allow the memory manually you could do something like :

Village **villages = new Village*[villageAmount];

Don't forget to free EVERY new, (If you only free villages, all the Village* that he contain will remain allocated.

Edit : someone else answered so I guess my answere is usless

edited Mar 15, 2019 at 0:45

answered Mar 15, 2019 at 0:35

Guillaume Magniadas

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2 Comments

Remy Lebeau Over a year ago

why are you using new for an array and not new[] instead? Village **villages = new Village*[villageAmount]; ... delete[] villages;

Guillaume Magniadas Over a year ago

Yes mybad, I was doing some C so I was still using malloc syntax

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