As already stated, qt4-x11 currently does not build on m68k due to using the generic atomics code. I'm currently working - tracked at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=660963 - at adding code to Qt for it to use GCC's builtin atomics (__sync_val_compare_and_swap() and friends), which either Debian or upstream already have done for the AVR32 platform, and support for which I backported on gcc-4.6 (our current workhorse compiler) but which is also available in gcc-4.7 from the FSF.

GCC's atomics code on Linux/m68k and Linux/ColdFire, with or without MMU, works by using a syscall (kernel helper) because the CPU's built-in compare-and-swap function is not reliably usable: there have been emulator bugs with it, it's said there are hardware bugs with it, not all CPUs have it (older 680x0 and all ColdFire), and it doesn't work on all platforms on all RAM types (e.g. Amiga ChipRAM). The Linux/m68k

maintainers say that to use the syscall is the way forward in all things atomic.

I'm opening this task here right now, so people interested can peek at it (and assign it to the correct Component, I choose Other because I don't know which one is right), and will report back with success once done