CODEWITHSUNDEEP
c++c++11gcccout
D1X
D1X

Reputation: 5474

Error "undefined reference to 'std::cout'"

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 7 (Wheezy).

Upvotes: 352

Views: 444853

Answers (6)

Serendipity
Serendipity

Reputation: 66

Adding the following line in your CMake makes gcc link with std and therefore recognize std::cout

target_link_libraries(your_project
        PRIVATE
        -lstdc++
        )

Upvotes: 2

shauryachats
shauryachats

Reputation: 10405

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

Upvotes: 484

user14093575
user14093575

Reputation:

Assuming code.cpp is the source code, the following will not throw errors:

make code
./code

Here the first command compiles the code and creates an executable with the same name, and the second command runs it. There is no need to specify g++ keyword in this case.

Upvotes: 11

netskink
netskink

Reputation: 4539

FWIW, if you want a makefile, here is how you can do either answer by switching the compiler at the top.

# links stdc++ library by default
# CC := g++
# or
CC := cc

all: hello

util.o: util.cc
        $(CC) -c -o util.o  util.cc

main.o: main.cc
        $(CC) -c -o main.o  main.cc

# notice -lstd++ is after the .o files
hello: main.o util.o
        $(CC) -o hello main.o util.o -lstdc++

clean:
        -rm util.o main.o hello

Upvotes: 0

iggy12345
iggy12345

Reputation: 1393

Makefiles

If you're working with a makefile and you ended up here like me, then this is probably what you're looking or:

If you're using a makefile, then you need to change cc as shown below

my_executable : main.o
    cc -o my_executable main.o

to

CC = g++

my_executable : main.o
    $(CC) -o my_executable main.o

Upvotes: 7

A B
A B

Reputation: 978

Yes, using g++ command worked for me: 

g++ my_source_code.cpp

Upvotes: 87

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