Segmentation Fault with malloc()

Question

In one part of my program I need to create a vector full of zeros the size of the user’s interval:

scanf("%ld %ld", &n1, &n2);
int *vetor; 
vetor = malloc((n2 - n1 + 1) * sizeof(long int));
for (long int k = 0; k <= n2; k++)
{
    vetor[k] = 0;
}

But when I type in a few ranges, like 10 1000000, the program gives Segmentation fault right away, what can be?

Answer 1

Use the calloc() and be happy.

scanf("%ld %ld", &n1, &n2);
int *vetor = calloc(n2 - n1 + 1, sizeof(long int));

I put in the Github for future reference.

When accessing the vector elements do not use the operator <=, use only the <, as it starts at 0, the last element is the size - 1, as you do to count 10 number starting from 0, you stop at 9.

Answer 2

scanf("%ld %ld", &n1, &n2);
int *vetor;
vetor = malloc(abs(n2 - n1+1) * sizeof(long int));
for ( k = 0; k <= abs(n2-n1); k++)
{
    vetor[k]=0;
}

I think I wanted to do it this way, we need to put the abs() because if we insert n1=100 and n2=1 would generate a negative number, which we don’t want, so we use the module.

Another way was to use the function calloc as already mentioned, but using the module.

int *vetor = calloc(abs(n2 - n1 + 1), sizeof(long int));