Velocity Reviews > Question : 3d array with pointer to pointer.

# Question : 3d array with pointer to pointer.

Joonshik Kim
Guest
Posts: n/a

 11-12-2006
I was trying to define 3d array with pointer to pointer. I wrote like
following.

int ***d;
nx = 3;
ny = 5;
nz = 4;

d = (int ***)malloc((int) nx*sizeof(int **));
*d = (int **)malloc((int) nx*ny*sizeof(int*));
**d = (int *)malloc((int) nx*ny*nz*sizeof(int));
for(i = 1; i < nx ; i++) d[i] = d[i-1] + ny;
for(i = 0; i < nx ; i++)
for(j = 1; j < ny ; j++) d[i][j] = d[i][j-1] + nz;

for(i=0 ; i < nx; i ++)
for(j = 0; j < ny; j++)
for(k = 0 ; k < nz; k++)
d[i][j][k] = 100*(i+1) + 10*(j+1) + k;

it compiled ok. but when I ran it, it shows error message like
"segementation fault.."

What did I do wrong ? can someone help me ?

thank you.

Richard Heathfield
Guest
Posts: n/a

 11-12-2006
Joonshik Kim said:

> I was trying to define 3d array with pointer to pointer. I wrote like
> following.
>
> int ***d;
> nx = 3;
> ny = 5;
> nz = 4;

d = malloc(nx * sizeof *d);
if(d == NULL) { HANDLE_THE_ERROR; }

for(i = 0; i < nx; i++)
{
d[i] = malloc(ny * sizeof *d[i]);
if(d[i] == NULL) { CLEAN_UP; HANDLE_THE_ERROR; }

for(j = 0; j < ny; j++)
{
d[i][j] = malloc(nz * sizeof *d[i][j]);
if(d[i][j] == NULL) { CLEAN_UP; HANDLE_THE_ERROR; }
for(k = 0; k < nz; k++)
{
d[i][j][k] = 42;

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: normal service will be restored as soon as possible. Please do not

Joonshik Kim
Guest
Posts: n/a

 11-12-2006
Oh..Thank you..
It works nice..

"Richard Heathfield" <(E-Mail Removed)> wrote in message
news(E-Mail Removed)...
> Joonshik Kim said:
>
> > I was trying to define 3d array with pointer to pointer. I wrote like
> > following.
> >
> > int ***d;
> > nx = 3;
> > ny = 5;
> > nz = 4;

>
> d = malloc(nx * sizeof *d);
> if(d == NULL) { HANDLE_THE_ERROR; }
>
> for(i = 0; i < nx; i++)
> {
> d[i] = malloc(ny * sizeof *d[i]);
> if(d[i] == NULL) { CLEAN_UP; HANDLE_THE_ERROR; }
>
> for(j = 0; j < ny; j++)
> {
> d[i][j] = malloc(nz * sizeof *d[i][j]);
> if(d[i][j] == NULL) { CLEAN_UP; HANDLE_THE_ERROR; }
> for(k = 0; k < nz; k++)
> {
> d[i][j][k] = 42;
>
>
> --
> Richard Heathfield
> "Usenet is a strange place" - dmr 29/7/1999
> http://www.cpax.org.uk
> email: normal service will be restored as soon as possible. Please do not

plodger@gmail.com
Guest
Posts: n/a

 11-15-2006
Richard Heathfield wrote:
[snip]
> --
> Richard Heathfield
> "Usenet is a strange place" - dmr 29/7/1999
> http://www.cpax.org.uk
> email: normal service will be restored as soon as possible. Please do not

Hi Richard, it's Sarah Thompson here. I've been trying to contact you
urgently, but haven't succeeded through usual channels, so many
apologies for posting here but I am not aware of any alternative.

You need to contact your brother Robert urgently in connection with a
family matter. Feel free to email me directly and I'll fill you in on
the details.

Best regards,
Sarah (thompson a t email dt arc dt nasa d t gov)

mark_bluemel@pobox.com
Guest
Posts: n/a

 11-15-2006

Joonshik Kim wrote:
> I was trying to define 3d array with pointer to pointer. I wrote like
> following.
>
> int ***d;
> nx = 3;
> ny = 5;
> nz = 4;
>
> d = (int ***)malloc((int) nx*sizeof(int **));

You store one address into d.

> *d = (int **)malloc((int) nx*ny*sizeof(int*));

You store one address at *d.

> **d = (int *)malloc((int) nx*ny*nz*sizeof(int));

You store one address at **d.

> for(i = 1; i < nx ; i++) d[i] = d[i-1] + ny;
> for(i = 0; i < nx ; i++)
> for(j = 1; j < ny ; j++) d[i][j] = d[i][j-1] + nz;

You now try to access 60 addresses. What is wrong with this picture?