Pharo, like its siblings Cuis, Squeak, and NewSpeak runs on a VM called Open Smalltalk. It is written in a stylized version of Smalltalk so can be debugged with the tandard Smalltalk tools (i.e. you can have the modified VM you're working on load and run an image - but your VM is running in a debugger!)
Then when you're happy with your revised VM, you can spit out portable C code, compile it, and BAM you've got a production VM! Most plug-ins and primitives are also written in the Smalltalk subset (called SLANG), so they will likely be similarly portable.
There is also an FFI for interfacing beyond the standard model.
Then when you're happy with your revised VM, you can spit out portable C code, compile it, and BAM you've got a production VM! Most plug-ins and primitives are also written in the Smalltalk subset (called SLANG), so they will likely be similarly portable.
There is also an FFI for interfacing beyond the standard model.