c - Heap allocate a 2D array (not array of pointers)

Question

I am writing C code and I would like to heap allocate 512*256 bytes. For my own convenience I would like to be able to access the elements with the syntax array[a][b]; no arithmetic to find the right index.

Every tutorial I see online tells me to create an array of pointers that point to arrays of the rows I want in my array. This means that each subarray needs to be malloc'd and free'd individually. I am interested in a solution that only requires one call to malloc and one call to free.(Thus all elements are contiguous) I think this is possible because I will not be constructing a jagged array.

I would appreciate if anyone could share the syntax for declaring such an array.

Answer 1

Well, if you want to allocate array of type, you assign it into a pointer of that type.

Since 2D arrays are arrays of arrays (in your case, an array of 512 arrays of 256 chars), you should assign it into a pointer to array of 256 chars:

char (*arr)[256]=malloc(512*256);
//Now, you can, for example:
arr[500][200]=75;

(The parentheses around *arr are to make it a pointer to array, and not an array of pointers)