Why does the installation of a 32-bit package remove 64-bit packages?

Question

It's not clear to me why the installation of a 32-bit package would necessitate the removal of a 64-bit package.

For example, if I try to install the 32-bit development package of libcurl with:

sudo apt-get install libcurl4-gnutls-dev:i386

apt-get indicates it will remove 17 different 64-bit packages, including gcc!

The following packages will be REMOVED:
  comerr-dev cpp g++ g++-multilib gcc gcc-multilib gfortran krb5-multidev
  libcurl4-openssl-dev libgcrypt11-dev libgnutls-dev libgpg-error-dev
  libidn11-dev libkrb5-dev libp11-kit-dev librtmp-dev libtasn1-6-dev

I need to utilise both 64-bit and 32-bit packages on the same development box. I believe this should be trivial. What am I misunderstanding? What do I need to do to install 32-bit packages without removing critical 64-bit packages?

Edit: Multiarch support already appears to be enabled:

$ dpkg --print-foreign-architectures
i386

Answer 1

If you use aptitude in interactive mode, you should be able to inspect the problem in the conflict editor (press e to enter it). Probably, one of the dependent libraries isn't yet multiarch-enabled.