无法使用gcc链接流代码

// writing on a text file
#include <iostream>
#include <fstream>
using namespace std;

int main () {
  ofstream myfile ("example.txt");
  if (myfile.is_open())
  {
    myfile << "This is a line.n";
    myfile << "This is another line.n";
    myfile.close();
  }
  else cout << "Unable to open file";
  return 0;
}

g++ -c -O2 -Wall -Wno-unused -fexceptions  -I. -I../../../stub -D_REENTRANT -D_THREAD_SAFE  -I.  -o t.o ./test.cc

g++ -o t -O2 -Wall -Wno-unused -fexceptions -Wl,-brtl -Wl,-blibpath:/lib:/usr/lib t.o -lpthreads

ld: 0711-224 WARNING: Duplicate symbol: .__divdi3
ld: 0711-224 WARNING: Duplicate symbol: .__moddi3
ld: 0711-224 WARNING: Duplicate symbol: .__udivdi3
ld: 0711-224 WARNING: Duplicate symbol: .__umoddi3
ld: 0711-224 WARNING: Duplicate symbol: .__udivmoddi4
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.

$ ./t
$ echo $?
0