libstdc++-dev:i386 cannot be installed on 64bit system.

[jcdutton]

lsb_release -rd
Description: Ubuntu precise (development branch)
Release: 12.04
uname -a
Linux inspiron1521 3.2.0-21-generic #34-Ubuntu SMP Fri Mar 30 04:25:35 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

I don't see why libstdc should try to install g++-4.6:i386
The 64bit version of gcc has the -m32 option to build 32bit binary output, even though compiling on a 64bit system.
So, in this case, installing libstdc++6-4.6-dev:i386 should just install the 32 bit lib and nothing else.
I can see the current multiarch allowing for 64bit and 32bit library files having the same filename, but I cannot see how you can have a 32bit gcc binary installed on a 64bit system, because the location and filename are the same.
Do we need to introduce /usr/bin and /usr/bin32, similar to /usr/lib32 and /usr/lib?

aptitude install libstdc++6-4.6-dev:i386

The following NEW packages will be installed:
  binutils:i386{ab} cpp-4.6:i386{ab} g++-4.6:i386{ab} gcc-4.6:i386{ab} libc6-dev:i386{a} libgmp10:i386{a} libgomp1:i386{a}
  libmpc2:i386{a} libmpfr4:i386{a} libquadmath0:i386{a} libstdc++6-4.6-dev:i386{b} linux-libc-dev:i386{a}
0 packages upgraded, 12 newly installed, 0 to remove and 0 not upgraded.
Need to get 29.1 MB of archives. After unpacking 82.6 MB will be used.
The following packages have unmet dependencies:
 g++-4.6 : Conflicts: g++-4.6:i386 but 4.6.3-1ubuntu3 is to be installed.
 g++-4.6:i386 : Conflicts: g++-4.6 but 4.6.3-1ubuntu3 is installed.
 gcc-4.6 : Conflicts: gcc-4.6:i386 but 4.6.3-1ubuntu3 is to be installed.
 gcc-4.6:i386 : Conflicts: gcc-4.6 but 4.6.3-1ubuntu3 is installed.
 libstdc++6-4.6-dev : Conflicts: libstdc++6-4.6-dev:i386 but 4.6.3-1ubuntu3 is to be installed.
 libstdc++6-4.6-dev:i386 : Conflicts: libstdc++6-4.6-dev but 4.6.3-1ubuntu3 is installed.
 cpp-4.6 : Conflicts: cpp-4.6:i386 but 4.6.3-1ubuntu3 is to be installed.
 cpp-4.6:i386 : Conflicts: cpp-4.6 but 4.6.3-1ubuntu3 is installed.
 binutils : Conflicts: binutils:i386 but 2.22-6ubuntu1 is to be installed.
 binutils:i386 : Conflicts: binutils but 2.22-6ubuntu1 is installed.

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[Matthias Klose (doko)]

multiarch doesn't handle co-installation of foreign binaries in /usr/bin

[jcdutton (james-superbug)]

I wished to install
libstdc++6-4.6-dev:i386
so that I could build a 32bit C++ program on a 64bit system.
This needs 64bit g++, and does not need 32bit g++,
so, libstdc++:i386 should not depend on g++:i386

Suggest:
32bit g++ depends on libstdc++
but don't make libstdc++:i386 require 32big g++

This would fix cross compiling 32bit C++ programs on a 64bit system.

[Matthias Klose (doko)]

just install g++-multilib

[Matthias Klose (doko)]

fixed for gcc-4.7 in raring, won't fix for gcc-4.6