I use gcc 2.3.3 to compile MiNT, and haven't had any problems running MultiTOS. The library version should not matter at all; if it does, then this represents either a serious bug in MiNT or one in the libraries. (In fact MiNT uses only a very few, very basic library functions.) I suppose it's time to remove all the remaining library calls from MiNT; that would at least eliminate one variable.