Portage currently provides no method for a user to start a failed compile without completely re-executing the src_compile() section of the ebuild. If your system has failed to compile due to some transient failure, then this is truly aggravating. It would be beneficial to at least provide a command which would cause the compilation step to be registered as if it had finished successfully. Example: gcc-3.1.1 compile breaks with an internal compiler error due to processor overheating. (I'm not kidding! It happened to me on my laptop on a hot day.) I go into the build directory and emake bootstrap-lean just as ebuild would. However, ebuild decides that the compile step has not been completed and when I try to ebuild install, it feels it needs to execute the compile step again. This feature would also aid in fixing bugs, IE, writing patches, as you could use the ebuild system to do your compiles while you test and avoid littering your system with unregistered installs.
processors that dont cool properly is actually quite common ... one way to control it is to set the load flag in the make var MAKEOPTS="-j2 -l1.3" in this case, make wont start new compiles if the load is higher than 1.3 another thing i do is background the compile every so often to let the load drop this is kind of a bug with processors that arent cooled properly ;)
There are other reasons that builds fail, power outages, for instance. The ability to resume a failed compile would be very attractive to users where the power grid fluctuates a lot.
FEATURES="noauto" ebuild .... compile install merge In general this is not a good idea. SegFaults normally aren't "Oops, I broke one this one specific thing, time to die" kinds of events... It's silent corruption until it breaks something. This is not something we want to leak into the system. The above should do what you want though. FEATURES can be set in make.conf