segmentation fault in a program with pointers and malloc

Question

Can anyone explain to me why I get a segmentation fault here?

(I'm writing a longer program that involves adding and multiplying matrices saved as dynamic arrays, but I tried to narrow down the scope of the program looking for the error - so don't worry that the excerpt below doesn't make too much sense, I just want to know what is wrong syntactically with it.)

int
main (void)
{
    int* a;
    int* c;
    int i,j,d;
    int n = 3;
    int m = n*n;
    a = (int*)malloc(m*sizeof(int));
    c = (int*)malloc(m*sizeof(int));
    a[0] = 1; a[1] = 4; a[2] = 3; a[3] = 2; a[4] = 2; a[5] = 2; a[6] = 0; a[7] = 1;
    a[8] = 0;

for (i = 0; i<n; ++i)
    {
    for (j = 0; i<n; ++j)
        {
        d = i*n + j;
        c[d] = a[d] + a[d];
        }
    }


 return 0;
}

Mitch Wheat · Accepted Answer · 2013-12-08 01:14:55Z

2

Second loop should use j not i in the terminating condition:

for (j = 0; i<n; ++j)
            ^

should be

for (j = 0; j < n; ++j)

answered Dec 8, 2013 at 1:14

Mitch Wheat

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Comments

Dave Rager · Accepted Answer · 2013-12-08 01:14:28Z

1

In your second loop you have the wrong conditional:

for (j = 0; i<n; ++j)

should be

for (j = 0; j<n; ++j)

answered Dec 8, 2013 at 1:14

Dave Rager

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