g++ - Missing include "bits/c++config.h" when cross compiling 64 bit program on 32 bit in Ubuntu

Question

I am running the 32bit version of Ubuntu 10.10 and trying to cross compile to a 64 bit target. Based on my research, I have installed the g++-multilib package.

The program is a very simple hello world:

#include <iostream>

int main( int argc, char** argv )
{
  std::cout << "hello world" << std::endl;
  return 0;
}

Compile:

g++ -m64 main.cpp

Error:

In file included from main.cpp:1:
/usr/include/c++/4.4/iostream:39: fatal error: bits/c++config.h: No such file or directory
compilation terminated.

I have found a c++config.h file but they reside under the i486-linux-gnu and i686-linux-gnu directories in /usr/include/c++/4.4/ There is not c++config.h in /usr/include/c++/bits.

Any ideas on what I am missing? Compiling without the -m64 flag works fine (a.out is created and runs correctly).

Edit Thanks to the hint from @nightcracker, I did a little more investigation into the include structure on the 32 and 64 bit systems. I have added an answer below that "fixes" the problem temporarily but I think it will break on the next update. Basically, I am missing a directory called /usr/include/c++/4.4/i686-linux-gnu/64 that should contain a subdirectory called bits that has the missing include file. Any idea what package should be taking care of this?

Answer 1

Adding this answer partially because it fixed my problem of the same issue and so I can bookmark this question myself.

I was able to fix it by doing the following:

sudo apt-get install gcc-multilib g++-multilib

If you've installed a version of gcc / g++ that doesn't ship by default (such as g++-4.8 on lucid) you'll want to match the version as well:

sudo apt-get install gcc-4.8-multilib g++-4.8-multilib