F'up of avr-gcc: New Features?
Perhaps the ability to squish up the vector table a little - an option to discard any sections of the vector table that aren't used so that normal program data can occupy them, which would reduce XMEGA application footprint. Or perhaps an option to use all unused entries in the vector table for normal data, so that you still save space even if you hook the first and last vector entries.
Vector table is realm of avr-libc (gcrt1.S constructs .vectors) and Binutils (linker script locates .vectors).
The tweak can be implemented by an own linker script and own startup code that work together, and linking with -nostartfiles.
I am not sure if this is a desired feature, because when an unimplemented IRQ fires, the application executes nonsense...
Under the assumption that "nonsense" can be statically detected and will be fixed during the development phase, it could be a reasonable feature.
But as I already said, avr-gcc (compiler driver, compiler proper and libgcc) can't do anything about it.