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undefined reference to 'std::cout'

Tags:

c++

gcc

c++11

cout

People also ask

Why is std :: cout not working?

This may happen because std::cout is writing to output buffer which is waiting to be flushed. If no flushing occurs nothing will print. So you may have to flush the buffer manually by doing the following: std::cout.

How do you fix a undefined reference in C++?

You can fix undefined reference in C++ by investigating the linker error messages and then providing the missing definition for the given symbols. Note that not all linker errors are undefined references, and the same programmer error does not cause all undefined reference errors.

How do you fix a undefined reference?

So when we try to assign it a value in the main function, the linker doesn't find the symbol and may result in an “unresolved external symbol” or “undefined reference”. The way to fix this error is to explicitly scope the variable using '::' outside the main before using it.


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