dynamic memory alloc and recursion

[crimsonalucard]

Below is a function I wrote used to evaluate the determinant of a nxn matrix. arguments are an array of the matrix values in order going from left to right jumping to the next line then going from left to right again.

An error happens after the function recursively calls itself once and attempts to allocate dynamic memory for a sub-matrix.

I'm not sure why this happens? Can anyone explain why an error occurs and how to correct it? Thanks.

double    evaluate(double  *mat,int      dim)
{
    //smallest case
    if(dim==2)
    {
        return mat[0]*mat[3]+mat[2]*mat[1];
    }
    //smallest case
    int b;
    double result = 0;
    //iterate through columns
    for(int j =0; j<dim; j++)
    {
        //calculate b
        if((j+2)%2==0)
        {
            b=1;
        }
        else
        {
            b=-1;
        }
        //calculate b
        //smaller matrix
        double *smaller = new double [(dim-1)*(dim-1)];//error occurs here after one recursive call
        int counter=0;
        for (int p = 0; p<dim*dim; p++)
        {
            if(dim != j)
            {
                smaller[counter]=mat[p];
                counter++;
            }
        }
 
        //smaller matrix
        result+=b*mat[j]*evaluate(smaller, dim-1); //recursive call
        delete [] smaller;
    }
    return result;
 
 
}
 

[RRick]

One probem you is that after you create a smaller matrix of dim-1**2 size (line 25), you then fill it up with dim**2 entries.

Since these values are on the stack, overwritting the stack like this can cause havoc with your program.