If you really just want the program to continue operating on dereferencing NULL pointers (and assuming that a NULL pointer is a pointer to address 0 in the VM,

If you really just want the program to continue operating on dereferencing NULL pointers (and assuming that a NULL pointer is a pointer to address 0 in the VM, which is a risky assumption to make) you can generally convince the OS to map address 0 to something valid, therefore making the access Just Work. Beyond that there are sometimes very valid reasons for allowing segfaults to occur in certain conditions and catching/patching them. For instance in an emulator's dynamic recompiler you could optimize your generated code by assuming that most memory accesses target the emulated RAM region (generally a reasonable assuption). Then you map the RAM buffer in such a way that if it turns out that the emulated program was actually attempting to access an address outside of RAM a memory fault occurs, which you can then catch and recompile the offending code block with a slower but more comprehensive address decode.