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I'm having a stack overflow allocating a huge matrix on the stack (and I agree with that: it's stupid to allocate it there) and I'm writing the following code since I want to access the matrix's elements with the subscripts indices mat[x][y]

double (*mul1)[N][N];
mul1 = new double[N][N];

I'm receiving an error: 

error C2440: '=' : cannot convert from 'double (*)[1000]' to 'double(*)[1000][1000]'

Why can't I allocate a bidimensional array with new?

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  • This is actually slightly different from the question someone linked as duplicate, because (I assume) N is known at compile time. You can do it with double (*mul1)[N]; and you avoid the pointer indirection that appears in the linked question for the nested arrays. (The key is that the * replaces one of the [], and new T[] returns a pointer to the first element.) Or you can write unique_ptr<double[][N]> mul1(new double[N][N]); and get automatic cleanup.
    – entheh
    Commented Mar 23, 2013 at 11:28

2 Answers 2

Reset to default
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You can do it like so:

int N = 10 ;
double** mul1 = new double*[N];
for(int i = 0; i < N; ++i)
   mul1[i] = new double[N];
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double *mul1[N];
for (int i=0;i<N;++i)
    mul1[i] = new double[N];

Representing a 2D array as a 1D array

Performance of 2-dimensional array vs 1-dimensional array

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  • error C2440: '=' : cannot convert from 'double (*)[1000]' to 'double **'
    – Johnny Pauling
    Commented Mar 23, 2013 at 11:25

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