undefined reference to 'std::cout'

Question

Shall this be the example:

#include <iostream>
using namespace std;
int main()
{
    cout << "Hola, moondo.\n";
}

It throws the error:

gcc -c main.cpp gcc -o edit main.o  main.o: In function `main':
main.cpp:(.text+0xa): undefined reference to `std::cout'
main.cpp:(.text+0xf): undefined reference to `std::basic_ostream<char,std::char_traits<char> >& std::operator<< <std::char_traits<char>>(std::basic_ostream<char, std::char_traits<char> >&, char const*)'
main.o: In function `__static_initialization_and_destruction_0(int,int)':
main.cpp:(.text+0x3d): undefined reference to `std::ios_base::Init::Init()'
main.cpp:(.text+0x4c): undefined reference to `std::ios_base::Init::~Init()' collect2: error: ld
returned 1 exit status make: *** [qs] Error 1

Also, this example:

#include <iostream>
int main()
{
    std::cout<<"Hola, moondo.\n";
}

throws the error:

gcc -c main.cpp gcc -o edit main.o  main.o: In function `main':
main.cpp:(.text+0xa): undefined reference to `std::cout'
main.cpp:(.text+0xf): undefined reference to `std::basic_ostream<char,std::char_traits<char> >& std::operator<<<std::char_traits<char>>(std::basic_ostream<char,std::char_traits<char> >&, char const*)'
main.o: In function `__static_initialization_and_destruction_0(int,int)': main.cpp:(.text+0x3d): undefined reference to `std::ios_base::Init::Init()'
main.cpp:(.text+0x4c): undefined reference to `std::ios_base::Init::~Init()' collect2: error: ld
returned 1 exit status make: *** [qs] Error 1

Note: I am using Debian Wheezy.

Try g++ instead of gcc. gcc is for C and will not give you access to the C++ standard library. — juanchopanza
Well, that definitely solved the problem. As I understand, GCC is the acronym for Gnu Compiler Collection. Shouldn't it call the g++ compiler when needed? So the command gcc calls the c compiler instead... — D1X
@D1X it's because you invoked the linker separately from the compiler. when you write gcc -o edit main.o it doesn't know that main.o is going to need C++ startup libraries. — M.M
Q: Shouldn't it call the g++ compiler when needed? A: No more than gcc should call gfortran, gjc, ... etc. etc. as needed. — paulsm4

shauryachats shauryachats · Accepted Answer · 2015-01-30T13:22:57

Compile the program with:

g++ -Wall -Wextra -Werror -c main.cpp -o main.o
     ^^^^^^^^^^^^^^^^^^^^ <- For listing all warnings when your code is compiled.

as cout is present in the C++ standard library, which would need explicit linking with -lstdc++ when using gcc; g++ links the standard library by default.

With gcc, (g++ should be preferred over gcc)

gcc main.cpp -lstdc++ -o main.o

undefined reference to 'std::cout'

4 Answers

Makefiles