C Increase char array of char array size

Question

I have a char array of char array like so:

char my_test[2][10];

As you can see I have a length of 2 and then 10. If I need to increase the first char array (2), how can this be done dynamically?

For example, half way through my application char[2] might be in use so therefore I need to use position 3 in the char array. I would then end up with this:

char store[3][10];

But keeping the data originally store in:

char store[0][10];
char store[1][10];
char store[2][10];

Answer 1

You should dynamically allocate memory for the array using standard C functions malloc and realloc declared in header <stdlib.h>.

Here is a demonstrative program that shows how the memory can be allocated.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define N   10

int main(void) 
{
    size_t n = 2;
    char ( *my_test )[N] = malloc( n * sizeof( char[N] ) );

    strcpy( my_test[0], "first" );
    strcpy( my_test[1], "second" );

    for ( size_t i = 0; i < n; i++ ) puts( my_test[i] );

    putchar( '\n' );

    char ( *tmp )[N] = realloc( my_test, ( n + 1 ) * sizeof( char[N] ) );

    if ( tmp != NULL )
    {
        my_test = tmp;
        strcpy( my_test[n++], "third" );
    }

    for ( size_t i = 0; i < n; i++ ) puts( my_test[i] );

    free( my_test );

    return 0;
}

The program output is

first
second

first
second
third