Undefined error Reference to Std

Question

#include <iostream>
using namespace std;
int main()
{
  int nombre, carre ;
  cout << "Introduza un numero : " ;
  cin >> nombre ;
  carre = nombre * nombre ;
  cout << "A raiz quadrada est ; " << carre ;
}

When I compile with GCC:

gcc -Wall -Wextra -Werror -o calc_carre calc_carre.cpp

Obtenho:

calc_carre.cpp:(.text+0xe): Undefined Reference to std::cout' calc_carre.cpp:(.text+0x13): undefined reference to Std::basic_ostream >&Std::Operator<< >(Std::basic_ostream >&, char const*)' calc_carre.cpp:(.text+0x1f): Undefined Reference to std::cin' calc_carre.cpp:(.text+0x24): undefined reference toStd::istream::Operator>>(int&)' calc_carre.cpp:(.text+0x3a): Undefined Reference to std::cout' calc_carre.cpp:(.text+0x3f): undefined reference to Std::basic_ostream >&Std::Operator<< >(Std::basic_ostream >&, char const*)' calc_carre.cpp:(.text+0x4f): Undefined Reference to std::ostream::operator<<(int)' /tmp/cclJ9vPR.o: In function __static_initialization_and_destruction_0(int, int)': calc_carre.cpp:(.text+0x7d): Undefined Reference to std::ios_base::Init::Init()' calc_carre.cpp:(.text+0x8c): undefined reference toStd::ios_base::Init::~Init()' collect2: error: Ld returned 1 Exit status

In the C:

#include <stdio.h>
int main()
{
  int nombre, carre ;
  printf ("Introduza un numero") ;
  scanf ("%d", &nombre) ;
  carre = nombre * nombre ;
  printf (" A sua raiz quadrada é: %d, nombre) ;
}

When I compile I get no mistake, but look through your eyes:

Answer 1

If you are using C++ with g++:

g++ -Wall -Wextra -Werror -o calc_carre calc_carre.cpp

If you want to gcc, which I don’t recommend, add the standard library:

gcc -lstdc++ -Wall -Wextra -Werror -o calc_carre calc_carre.cpp

In C there is error too:

#include <stdio.h>
int main() {
    int nombre, carre ;
    printf("Introduza un numero");
    scanf("%d", &nombre);
    carre = nombre * nombre;
    printf("A sua raiz quadrada é: %d", carre);
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

This code is obviously not calculating the square root, but then it’s just mathematics.