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).
87 Answers
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 Yes, using g++ command worked for me:
g++ my_source_code.cpp 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.
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 Adding the following line in your CMake makes gcc link with std and therefore recognize std::cout
target_link_libraries(your_project PRIVATE -lstdc++ ) I was having the same error then I compile code using g++ filename.cpp -o temp
where I put filename replace it with you file and on temp it whatever name you want ,after that run with with ./temp replace with name you used
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 
