__GNUC- Set this to "" (the empty string), and
exportit. This causes GCC to be used as the main compiler. Studio takes its place as the "shadow compiler".
CW_NO_SHADOW- Set this to 1 to prevent the shadow compiler from running (for instance, if you do not have Studio at all).
See 2012-06-15 Illumos will now build with GCC 4.4.4 + patches for details on configuration for building with GCC 4.4.4.
Note that this has been tested considerably less than building with Sun Studio (both the build, and the resulting software), so if you experience bugs please mention that the software you are running was built using GCC, and which version (3.4.3 or 4.4.4).
For the moment we still require that contributed changes build with Sun Studio as the compiler. We understand that the required version of Sun Studio is no longer publicly available and will accept contributions that were tested only with GCC. For the time being, GCC 3.4.3 is the primary compiler for GCC builds (i.e. your integrations should not break full builds with this compiler), but after a while GCC 4.4.4 is likely to be promoted to this role.
Preparing build tools
A few tools have to be prepared before we can build the rest of illumos. To build them, you should run commands in a new shell which sets some environment variables: