undefined reference to 'std::cout'

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

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