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I am trying to split a string delimited by '\n' into an array of strings. The string represents an NxN rectangle so each row on the matrix will contain the same number of characters. This is what I have tried:

char    **string_to_tab(char *str, int width, int height)
{
    int     i; //counter to scan str
    int     x; //counter for tab column no.
    int     y; //counter for tab row no.
    char    **tab;

    i = 0; //I initialise variables
    x = 0; //separately because I
    y = 0; //like to :P
    tab = (char**)malloc(sizeof(char) * height * width);
    while (y < height)
    {
        while (x < width)
        {
            if (str[i] != '\n' || !(str[i]))
                {
                    tab[y][x] = str[i]; //assign char to char* array
                    x++;
                }
            i++;
        }
        x = 0;
        y++;
    }
    return (tab);
}

This gets me a segmentation fault, calling it would look something like this:

char *str = "+--+\n|  |\n|  |\n+--+";
char **matrix = string_to_tab(str, 4, 4);
Martin James
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Cuan Clifford
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1 Answers1

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Your variable tab is a pointer to a pointer, but you reserve a single array of characters with malloc. If you want to use tab as an array of pointers as in your code, you have to allocate an array of char pointers first, and then allocate an array of char for each row. But this is complicate.

It should be easier to use char *tab; instead, and allocate just an an array of characters as your code does already. You have to change the element access to tab[y * width + x] instead of tab[y][x].

clemens
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    Thank you, your response helped me a lot. I now understand how memory is assigned to n-dimensional arrays a lot better. – Cuan Clifford Jan 28 '18 at 11:07