‘cout’ is not a member of ‘std’ & ‘cout’ was not declared in this scope

Question

I realize that there are several duplicates like this but none of them have worked for me so far. I am trying to compile a C++ very simple program on Ubuntu using g++ but it is giving me scope errors.

#include <iostream>
using namespace std;

int main()
{
  cout << "Hello world";
}

This gives me this error:

sudo g++ -v test.c
test.c: In function ‘int main()’:
test.c:7:3: error: ‘cout’ was not declared in this scope

I also tried defining the scope as many other posts say, but that also didn't work, but gave me a different error:

#include <iostream>

int main()
{
  std::cout << "Hello world";
}

Gives error:

test.c: In function ‘int main()’:
test.c:6:3: error: ‘cout’ is not a member of ‘std’

Most of the suggestions online suggest "using namespace std;", "#include " and "std::cout". So I tried all 3 together, still no luck :(

#include <iostream>
using namespace std;

int main()
{
  std::cout << "Hello world";
}

gives error:

test.c: In function ‘int main()’:
test.c:7:3: error: ‘cout’ is not a member of ‘std’

---

I have gone through several forums online but none of them seem to work for me :(

This is a part of a bigger issue because of which one of my linux make doesn't work.

Btw, I am using g++ and not gcc as a few posts messed up.

---

EDIT 1:

I changed the name to .cpp, and execute without sudo. Here is the verbose output:

pranoy@pranoyubuntu1210:~/Desktop/SIP/SIPp/sipp-3.3$ g++ -v test.cpp -o test
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.7/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.7.2-2ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs --enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.7 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.7.2 (Ubuntu/Linaro 4.7.2-2ubuntu1) 
COLLECT_GCC_OPTIONS='-v' '-o' 'test' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /usr/lib/gcc/x86_64-linux-gnu/4.7/cc1plus -quiet -v -imultiarch x86_64-linux-gnu -D_GNU_SOURCE test.cpp -quiet -dumpbase test.cpp -mtune=generic -march=x86-64 -auxbase test -version -fstack-protector -o /tmp/cczzibvL.s
GNU C++ (Ubuntu/Linaro 4.7.2-2ubuntu1) version 4.7.2 (x86_64-linux-gnu)
    compiled by GNU C version 4.7.2, GMP version 5.0.2, MPFR version 3.1.0-p3, MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/c++/4.7
 /usr/include/c++/4.7/x86_64-linux-gnu
 /usr/include/c++/4.7/backward
 /usr/lib/gcc/x86_64-linux-gnu/4.7/include
 /usr/local/include
 /usr/lib/gcc/x86_64-linux-gnu/4.7/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
GNU C++ (Ubuntu/Linaro 4.7.2-2ubuntu1) version 4.7.2 (x86_64-linux-gnu)
    compiled by GNU C version 4.7.2, GMP version 5.0.2, MPFR version 3.1.0-p3, MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 521527ea42f0901bf839bcaad0cb13e6
test.cpp: In function ‘int main()’:
test.cpp:5:3: error: ‘cout’ is not a member of ‘std’

Solution 1

What you've written works absolutely fine on my Ubuntu system, with the same version of g++.

It sounds like you haven't installed all of the necessary files for the C++ environment, or something isn't quite right with it. Try this:

$ sudo apt-get remove g++ libstdc++-6.4.7-dev
$ sudo apt-get install build-essential g++-multilib

(Run dpkg -l | grep libstdc++ to get the exact version of libstdc++ if the above fails)

Solution 2

This isn't the case for this, but could be an answer to "error: ‘cout’ is not a member of ‘std’". I came here looking for help, so this might help someone else.

If you have a header file (header.h) where the last function/class declaration does not have a semi-colon after it:

#include <string>

function(std::string str)

And your c++ file includes this before iostream:

#include "header.h"
#include <iostream>

The function/class (function in this case) messes up the declarations in iostream. #include basically just pastes the text into the code. Adding the semi-colon can fix the problem.

Solution 3

(C++, Linux Terminal, no compiling error, but no prints into the Terminal), maybe try:

$ g++ yourcode.cpp
$ ./a.out

first line: g++ compiles your code.
second line: runs your compiled code.

Solution 4

For C++ programs, use g++, not gcc. If you get errors that suggest your compiler cannot find the standard library, that's because you probably used gcc.

Solution 5

Rename file extension with .cpp .

Compile source code by command

gcc source.cpp -o output.out

GCC will automatically compile it as a C++ program.

View more solutions

Comments

[Andreas Fester]

I think this is the best advice we can give - you should probably also suggest to reinstall the corresponding libstdc++-dev package, in case the include files are messed up (can not check the proper version currently, but should be something like libstdc++6-4.7-dev)

[sudoExclaimationExclaimation]

@Andreas I installed it as a part of the build-essential as far as I can remember. I will try to reinstall them with your commands and see if it works. Thanks to both of you for the help so far! :)

[sudoExclaimationExclaimation]

@Andreas It worked!! Now I can run my code! Something was mseed up while installing g++. Instead of remove, I purged it to remove all the files as well. Then reinstalled it. 'sudo apt-get purge g++ libstdc++6-4.7-dev' 'sudo apt-get install build-essential g++-multilib' You guys are the best! :) THanks!

[sudoExclaimationExclaimation]

you are answering a 2 year old question which is already answered. OP was already using g++ not gcc.