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Function using dynamic mem. allocation - getting seg. fault

leo255 (139)
Hi all,

I pretty much just want the nonzeroCopy function to return a pointer to an array of something, except without all the zero's. This is, of course, done with dynamic memory allocation. I'm getting a seg. fault here, and I'm not sure why.

Would really appreciate the guidance here.

Thanks.

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#include <iostream>
#include <cstdlib>

using namespace std;

int * nonzeroCopy( unsigned & nonzeroEls, const int a[], unsigned els );
void show( const int a[], unsigned elements );
void die(const string & msg);

int main(){

unsigned nonZeroElsIn;
int arr2[4] = {4, 0, 0, -6};

int * newArr2 = nonzeroCopy(nonZeroElsIn, arr2, 4);
show(newArr2, nonZeroElsIn);

}

int * nonzeroCopy( unsigned & nonzeroEls, const int a[], unsigned els )
{

    for (int i = 0; i < els; i++)
    {
        if (a[i] != 0)
        nonzeroEls++;
    }

    int * newNonZeroArr;

    try
    {
        newNonZeroArr = new int[nonzeroEls];

    for (int i = 0; i < nonzeroEls; i++)
    {
        if (a[i] != 0)
        newNonZeroArr[i] = a[i];
    }

    }

      catch(const bad_alloc &)
    {
        die("nonZeroCopy: Alloc Failure");
    }

    return newNonZeroArr;
}

void show( const int a[], unsigned elements )
{

    for (int i = 0; i < elements; i++)
        cout << a[i] << endl;

}

void die(const string & msg)
{
    cerr << "Fatal error: " << msg << endl;
    exit(EXIT_FAILURE);
}
keskiverto (10365)
What is the value of nonZeroElsIn just before you call nonzeroCopy()?
How will nonzeroCopy() change that value?

Line 38. Your sample data performs these:
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newNonZeroArr[0] = 4;
newNonZeroArr[3] = -6;

The latter reveals the error in logic, doesn't it?
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