how to malloc an int * in C - c

Question

I want to make a fucntion that load a map in a char ** and return it.
To do this I need to make a function that return an int * with inside it, the length of each line in a char ** give as arguments.
my problem is, it keep segfault and I don't know how to fix this.
when I use valgrind the errors are :
Use of uninitialised value of size 8 ,
Invalid write of size 1
int *nb_cols_pline(char *filepath) //length of each line in char **
{
int x, y = 0;
struct stat *size = malloc(sizeof(struct stat));
stat(filepath, size);
int *count = malloc(sizeof(int) * nb_lines(filepath)); //first errors may be here
int fd = open(filepath, O_RDONLY);
char *buffer = malloc(sizeof(char) * size->st_size);
read(fd, buffer, size->st_size);
for (y = 0; y < nb_lines(filepath); y++) {
for (x = 0; buffer[x] != '\n'; x++) {
}
count[y] = x; //maybe second error
}
close(fd);
free(size); free(buffer);
return count;
}
char **load_map(char *filepath)
{
int i = 0;
struct stat *size = malloc(sizeof(struct stat));
stat(filepath, size);
int *nb_cols = malloc(sizeof(int) * nb_lines(filepath));
char *buffer = malloc(sizeof(char) * size->st_size);
for (int x = 0; x < nb_lines(filepath); x++) {
nb_cols[x] = nb_cols_pline(filepath)[x];
}
char **map = malloc(sizeof(char *) * nb_lines(filepath) + 1);
for (int x = 0; x < nb_lines(filepath); x++) {
map = malloc(sizeof(char) * nb_cols[x]);
}
int fd = open(filepath, O_RDONLY);
read(fd, buffer, size->st_size);
for (int y = 0; y < nb_lines(filepath); y++) {
for (int x = 0; x < nb_cols[i]; x++) {
map[y][x] = buffer[i];
i += 1;
}
i += 1;
}
close(fd);
free(buffer); free(nb_cols); free(size);
return map;
}