test% cc -D_KERNEL -c xx1.ctest% cc -D_KERNEL -c xx2.ctest% ld -r -o xx xx1.o xx2.o
The _KERNEL symbol must be defined while compiling kernel (driver) code. No other symbols (such as sun4c or sun4m) should be defined, aside from driver private symbols. DEBUG may also be defined to enable any calls to ASSERT(9F). There is also no need to use the -I flag for the standard headers.
Once the driver is stable, optimization flags can be used. For the Sun WorkShop Compiler C, the normal -O flag, or its equivalent -xO2, may be used. Note that -xO2 is the highest level of optimization device drivers should use (see cc(1)).
Running ld -r is necessary even if there is only one object module.