how can i have a struct have an unknown size array member?

Question

im trying to make a sort of minesweeper clone in c, but i cant figure out how to create a variable length array member of a struct and initialize it.

my struct definitions

typedef struct Cell
{
    Rectangle area;         // The area the cell covers
    bool hasMine;           // If the cell covers a mine
    bool covered;           // If the cell is currently covered
    int touching;           // How many mines the cell is touching
} Cell;

typedef struct Minefield
{
    int columns;        // The amount of columns
    int rows;           // The amount of rows
    int mines;          // The amount of mines
    Cell field[];       // An array of columns*rows Cells

} Minefield;

how im creating new instances of a Minefield

Minefield NewGame(int columns, int rows, int mines)
{
    int i = 0;

    Cell cells[columns*rows];

    for (i=0; i < columns*rows; i++) {
        int x = 0;
        int y = 0;

        if (i == 0) {
            Rectangle area = (Rectangle){0, 0, cellsize, cellsize};
            cells[i] = (Cell){area, false, true, 0};
        }
        else {
            Cell previous = cells[i-1];

            x = previous.area.x + cellsize;
            y = previous.area.y + cellsize;

            Rectangle area = (Rectangle){x, y, cellsize, cellsize};
            cells[i] = (Cell){area, false, true, 0};
        }
        
    }

    Minefield field = (Minefield){columns, rows, mines, cells};
    return field;
}

im new to c, ive done some googling and ive come across some very similar questions, but i cant really understand them or the examples they give. i think you can do what my errendous code is trying to do (or something very similar) with a gcc extension, but i want my code to be portable. how can i have a struct have an unknown size array member?

Answer 1

Unfortunately, C doesn't have any built-in dynamic array like python. However, if you want to use some dynamic array either you can implement your self or you can see the answer to that link C dynamically growing array which explains that you need to have starting array with a default size, and then you can increase the size of the array which depends on your algorithm. After you import that header file provided by @casablance, you can simply use it for your minesweeper game.