Why does this 2[d] array crash when 'fill' command is used?

[RubyDave]

class b {
    public:
        string boardinfo[3][3];
} o_tic;

fill(&o_tic.boardinfo[0][0], &o_tic.boardinfo[0][0] + sizeof(o_tic.boardinfo), "-");

Any insight as to why this crashes on runtime?

EDIT:

NVM I changed "sizeof(o_tic.boardinfo)" to "3*3"