Edit a 2D array through a function in C - c

Question

I have this function :
void foo( char tab[8][8] )
I want this function to edit the values of the tab array, so i tried theses syntax :
void foo( char *(*tab)[8][8] )
void foo( char *(tab)[8][8] )
void foo( char **tab )
And a LOT of others. I always get a fail while compiling, like this one :
error: cannot convert 'char ()[8][8]' to 'char (*)[8][8]' for argument '1' (...)
So, my quesiton is : how to create and pass to a function a pointer to a 2D array ?
Thanks.

Answer 1

This time try to declare your function as
void foo( char (*tab)[8] );
and call it as
foo(point);
Note that in this case you need to pass only array name as it decays to pointer when passed to a function (some exceptions are there). After decay it is of type char (*)[8].
You can do it also by declaring
void foo( char (*tab)[8][8] );
and call it as
foo(&point);
In this case notice that I passed &poinnt, i.e, address of the entire array which is of type char (*)[8][8].
Sample:
void foo(char (*tab)[8][8])
{
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < 68j++)
{
scanf("%d", &(*tab)[i][j]);
}
}
}

Answer 2

With an array, you can always modify the data in the function because what is passed is a pointer (in the absence of const qualifiers, of course). That is, you could write:
void foo(char tab[8][8])
{
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < 8; j++)
tab[i][j] = (x + y) % 2 : 'X' : 'O';
}
}
And call it:
void calling_func(void)
{
char board[8][8];
foo(board);
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < 8; j++)
putchar(tab[i][j]);
putchar('\n');
}
}
You can get the error messages you were seeing if you write:
foo(&board);
That passes a pointer to an array to the function. For that to work, you have to rewrite the function as:
void foo(char (*tab)[8][8])
{
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < 8; j++)
(*tab)[i][j] = (x + y) % 2 : 'X' : 'O';
}
}
However, this is seldom the correct way to write the code. Use the first alternative until this is forced upon you (which probably won't be this year — I don't recall having to use a pointer to an array except to answer questions on SO, but maybe it was such a ghastly experience that I have forgotten all about it).