On Mac OS X 10.5 the default compiler is GCC 4.0.1, Apple does provide GCC 4.2.1 as part of the XCode Developer Tools releases for 10.5 but it isn’t setup as the default.

The main tools are located in /usr/bin. In this folder you will find both gcc 4.0 and 4.2 along with g++ 4.0 and 4.2. The commands gcc, g++, cc, and gcov are all symbolic links to the default 4.0 versions. To make 4.2 the default we just need to modify the symbolic links.

To do this we need to go in to the Terminal and issue the following commands:

cd /usr/bin
sudo ln -Fs c++-4.2 c++
sudo ln -Fs gcc-4.2 cc
sudo ln -Fs g++-4.2 g++
sudo ln -Fs gcc-4.2 gcc
sudo ln -Fs gcov-4.2 gcov

Now you should have a complete working gcc 4.2.1 tool chain. If there is a problem you can verify the symbolic links are pointing at the correct targets by typing ls -l Hope this helps someone else.