Function igraph_matrix_char_search 

pub unsafe extern "C" fn igraph_matrix_char_search(
    m: *const igraph_matrix_char_t,
    from: igraph_int_t,
    what: c_char,
    pos: *mut igraph_int_t,
    row: *mut igraph_int_t,
    col: *mut igraph_int_t,
) -> igraph_bool_t