Variable-sized object may not be initialized problem in array

Question

When I try to run this simple code, it returns a Variable-sized object may not be initialized error. I have no idea why and how to resolve this problem.

int main()
{
    int n=0;
    n=1;
    int a[n]={}, b[n]={};
    return 0;
}

Variable length arrays are a non-standard compiler extension. You should use std::vector instead or make n const. — 0x5453
– 0x5453, Commented Apr 24, 2020 at 13:06
Does this answer your question? Variable Length Array (VLA) in C++ compilers — bitmask
– bitmask, Commented Apr 24, 2020 at 13:22

Icebone1000 · Accepted Answer · 2020-04-24 13:16:37Z

2

The array lenght must be known at compile time. Either

int a[1];

or

constexpr int n = 1;
int a[n];

Otherwise you need a dynamic array like the std container std::vector.

answered Apr 24, 2020 at 13:16

Icebone1000

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Comments

NutCracker · Accepted Answer · 2020-04-24 13:15:53Z

0

You can initialize your array properly with the std::fill_n like:

std::fill_n(a, n, 0);
std::fill_n(b, n, 0);

or use std::vector like:

std::vector<int> a(n);

It will initialize all the elements to 0 by default.

Or, you can have something like:

constexpr size_t n = 10;
int a[n]{};

This will also initialize all the elements to 0.

edited Apr 24, 2020 at 13:15

answered Apr 24, 2020 at 13:07

NutCracker

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Comments

user14157591 · Accepted Answer · 2020-08-25 02:29:59Z

0

Try this:

const int n=1;

int main()
{
    int a[n]={}, b[n]={};
    return 0;
}

The above code will let you create an array with length n. Note: n can't be changed.

answered Aug 25, 2020 at 2:29

user14157591

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