When JVM crashed unexpectedly, it could leave a coredump file for further debugging and diagnosis. We have to type many tedious instructions when debugging. For example, in order to get the name of InstanceKlass, we should:

print (char*)((InstanceKlass*)0x123)->_name->_body

We can predefine gdb functions to provide these functions, just like what src/hotspot/share/gc/z/zDebug.gdb did, which can facilitate debugging and problem diagnosis.