Undefined symbols for architecture x86_64: Which architecture should I use?

Question

I'm trying to do some really simple stuff in C++, but I can't find any information on how to tackle this. Even the book I have just says "Just compile and run the program".

test.cpp

#include <iostream> 
using namespace std;

int main() 
{ 
    cout << "Never fear, C++ is here!"; 
    return 0;
}

The compiler says:

Undefined symbols for architecture x86_64:
  "std::cout", referenced from:
      _main in ccVfJHGs.o
  "std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)", referenced from:
      _main in ccVfJHGs.o
  "std::ios_base::Init::Init()", referenced from:
      __static_initialization_and_destruction_0(int, int)in ccVfJHGs.o
  "std::ios_base::Init::~Init()", referenced from:
      ___tcf_0 in ccVfJHGs.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

I tried compiling with flags like -arch i386 and -m32 but it always says it's the wrong architecture. Which one should I use?

I'm doing this on a Mac but not using XCode, just gcc.

Which gcc do you use? Macports? XCode? Looks like your path is messed up. — FFox, Nov 07 '11 at 09:20

score 103 · Accepted Answer · answered Nov 07 '11 at 09:20

103

The error isn't that it's the wrong architecture, it's that std::cout (and other symbols) isn't defined.

You should compile and link with g++ not gcc, to automatically link with correct C++ libraries.

answered Nov 07 '11 at 09:20

Some programmer dude

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Oh, thanks! Why isn't gcc working for me? Every example I see is using gcc, is it a os x thing? – oskob Nov 07 '11 at 09:31
3

@oskob No, it's simply because gcc is the C compiler (though it handles C++ syntax), and g++ is the C++ compiler. – Some programmer dude Nov 07 '11 at 09:33
Isn't gcc a front-end which will delegate to g++ when it encounters .cc / .cpp files? – RobH Nov 07 '11 at 10:55
17

`g++` passes `-lstdc++` to the linker, `gcc` doesn't and that's the only difference. – Maxim Egorushkin Nov 07 '11 at 11:08
Thank you! You just saved me a bunch of time! – Mister R2 May 18 '13 at 04:23

score 5 · Answer 2 · answered Nov 07 '11 at 10:50

5

The error is caused because you're compiling with gcc, which only default-links libc. You need to compile with g++ so that libstdc++ is auto-linked in too.

answered Nov 07 '11 at 10:50

moshbear

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score 2 · Answer 3 · answered Aug 29 '16 at 17:29

2

Use g++ instead of gcc to link with exact c++ libraries

answered Aug 29 '16 at 17:29

Muhammed Shibin

37
3

This is a comment rather than an answer. Please obtain the rep to post it as such. – Mad Physicist Aug 29 '16 at 17:48

Undefined symbols for architecture x86_64: Which architecture should I use?

3 Answers3

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