How can i malloc a char ** - c

Question

I have to code a battleship game for school so i'm trying to generate the map on which the players are going to place their boats, i have a segfault but i don't see why.
Here's my code :
Main :
int main(int ac, char **av)
{
map_data map_data;
print_map(map_gen(map_data));
return(0);
}
Struct :
typedef struct map_data {
int lines;
int letters;
int width;
int height;
}map_data;
Map generation :
char **map_gen(map_data map_data)
{
map_data.lines = 0;
map_data.width = 18;
map_data.height = 10;
map_data.letters = 65;
char **map = malloc(sizeof((char)18 * 10));
for (int s = 0; s <= map_data.height ; s++) {
for (int c = 0; c <= map_data.width; c++) {
map_fill(map, map_data, s, c);
}
}
return (map);
}
Filling of the char **map :
void char_fill(char **map, char ch, int s, int c)
{
map[s][c] = ch;
}
void map_fill(char **map, map_data map_data, int s, int c)
{
if (c == 1)
char_fill(map, '|', s, c);
if (s == 1)
char_fill(map, '-', s, c);
if (c == map_data.width)
char_fill(map, '\n', s, c);
map_fill2(map, map_data, s, c);
}
int map_fill2(char **map, map_data map_data, int s, int c)
{
if (s == 0 && c == 0)
char_fill(map, ' ', s, c);
if (s == 1 && c == 1)
char_fill(map, '+', s, c);
if (c > 1 && c % 2 == 0)
char_fill(map, '.', s, c);
if (s > 1 && c % 2 == 1)
char_fill(map, ' ', s, c);
if (s == 10 && c == 18)
char_fill(map, '\0', s, c);
if (s > 1 && c == 0) {
char_fill(map, my_int_to_char(map_data.lines), 0, 0);
map_data.lines = map_data.lines + 1;
}
if (!map[s][c]) {
my_putstr("error filling the map, please try again.");
return (EXIT_FAILURE);
}
}
Print :
void print_map(char **map)
{
int h = 0;
int w = 0;
while (map[h][w] != '\0') {
while (map[h][w] != '\n') {
my_putchar(map[h][w]);
w = w + 1;
}
h = h + 1;
}
}
Am i doing something wrong ?
Any tips on how to improve my code ?
Thanks

Answer 1

you do not need a pointer to pointer only 2D array for it.
Use the correct types.
Wrap the data into your structure. Do noy use separate data structures without need
Indexes in C atart from 0.
typedef struct map_data {
size_t lines;
size_t letters;
size_t width;
size_t height;
char map[];
}map_data;
int map_fill2(map_data *map, size_t s, size_t c);
void char_fill(map_data *map, char ch, size_t s, size_t c)
{
char (*cmap)[map -> width] = (char (*)[map -> width])map -> map;
cmap[s][c] = ch;
}
void map_fill(map_data *map, size_t s, size_t c)
{
if (c == 0)
char_fill(map, '|', s, c);
if (s == 0)
char_fill(map, '-', s, c);
if (c == map -> width - 1)
char_fill(map, '\n', s, c);
map_fill2(map, s, c);
}
int map_fill2(map_data *map, size_t s, size_t c)
{
char (*cmap)[map -> width] = (char (*)[map -> width])map -> map;
if (s == 0 && c == 0)
char_fill(map, ' ', s, c);
if (s == 1 && c == 1)
char_fill(map, '+', s, c);
if (c > 1 && c % 2 == 0)
char_fill(map, '.', s, c);
if (s > 1 && c % 2 == 1)
char_fill(map, ' ', s, c);
if (s == 10 && c == 18)
char_fill(map, '\0', s, c);
if (s > 1 && c == 0) {
char_fill(map, my_int_to_char(map -> lines), 0, 0);
map -> lines += 1;
}
if (!cmap[s][c]) {
puts("error filling the map, please try again.");
return (EXIT_FAILURE);
}
return 0;
}
map_data *map_gen(size_t lines, size_t letters, size_t width, size_t height)
{
map_data *map = malloc(sizeof(*map) + width * height * sizeof(map -> map[0]));
if(map)
{
map -> width = width;
map -> lines = lines;
map -> letters = letters;
map -> height = height;
for (size_t s = 0; s < height ; s++)
{
for (size_t c = 0; c < width; c++)
{
map_fill(map, s, c);
}
}
}
return (map);
}

Answer 2

At least this issue:
sizeof((char)18 * 10) is the sizeof an int, likely 4.
Allocate to the size of the referenced object times the number needed.
// char **map = malloc(sizeof((char)18 * 10));
char **map = malloc(sizeof *map * map_data.height);
Then allocate for each row
// Note <, not <=
for (int row = 0; row < map_data.height; row++) {
map[row] = malloc(sizeof *(map[row]) * map_data.width);
for (int col = 0; col < map_data.width; col++) {
map_fill(map, map_data, row, col);
}
}
Robust code would also check for allocation failures.