Kernel builds with gcc
The recommended compiler for building Linux 2.4 is gcc 2.95. New compilers upto gcc 3.3 have been used successfully to build the kernel however with gcc 3.4 there may be problems when certain configurations. With Linux 2.4 being in deep freeze mode we generally don't intend to fix such problems but rather recommend to use an older compiler for the kernel.
The latest "official" GCC 2 is version 2.95.3. The GCC 2.96 is unofficial massively patched version. It provides more efficient optimization with -O2, more strict syntax checkhing and supports more recent C++ standarts. Unfortuntely, C++ ABI is not compatible with "official" 2.95.3 nor 3.0.
Any gcc version between 3.0 and 3.4 may be used and is fully supported. Gcc 4.0 is still considered experimental at this point so not recommended where reliability.
At December, 2005 Andrew Morton has dropped a support for 2.95 in the Linux 2.6 . See a discussion.