GCC for Windows 64 & 32 bits
To install just the 32-bit or just 64-bit compiler with dependencies, use:
sudo port install i686-w64-mingw32-gcc sudo port install x86_64-w64-mingw32-gcc
A shortcut to install both:
sudo port install mingw-w64
Here is the list of Mingw-w64 packages on MacPorts.