How to use malloc on a 2D integer array

Question

How do I define a 2D array where the first dimension is already defined with MAX_VALUES. I wish to be able to allocate memory to the second dimension. Below is what I have attempted. I want an array with A[1000][mallocd]

#define MAX_VALUES 1000
int
main(){
    int n= 10;
    int *A[MAX_VALUES] = malloc(10 * sizeof(int));

}

Your A has the wrong type, the * binds to the left. You want int (*A)[MAX_VALUES]. — Jens Gustedt
– Jens Gustedt, Commented Jun 5, 2015 at 17:14

haccks · Accepted Answer · 2015-06-05 15:24:01Z

2

Try this

int (*A)[n] = malloc(MAX_VALUES * sizeof(*A));

It will allocate contiguous 2D array.

answered Jun 5, 2015 at 15:24

haccks

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Buddha · Accepted Answer · 2015-06-05 15:24:03Z

1

try this :

int*A[MAX_VALUES],n;
for(i=0;i<MAX_VALUES;i++)
  A[i]=malloc(n*sizeof(int);

It will have MAX_VALUE rows with number of coloumns mallocked.

answered Jun 5, 2015 at 15:24

Buddha

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1 Comment

Jens Gustedt Over a year ago

This doesn't allocate a 2D array but several separate arrays. @haccks answer gives the correct approach.

Eugene Sh. · Accepted Answer · 2015-06-05 15:25:57Z

1

int *A[MAX_VALUES] is an array of int pointers, which is already statically allocated. If you want to allocate some space pointed by each one of the pointers you will have to iterate on the array and assign each pointer with a different malloc. Otherwise you will have to redefine your A (as @haccks answer is suggesting, for example).

answered Jun 5, 2015 at 15:25

Eugene Sh.

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