/in/foo.cc: In function 'int main()':
/in/foo.cc:68:22: warning: 'p' may be used uninitialized in this function [-Wmaybe-uninitialized]
    updata_elem(p,val);
                      ^
/in/foo.cc:68:22: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
/in/foo.cc:73:21: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
    output_sum(l,r,n);
                     ^
/in/foo.cc:73:21: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]