Well, there is the Object Memory as defined in the Bluebook, but otherwise it's file based. There are important differences to Smalltalk-80, where even the compiler and the scheduler are part of an "eternal" (i.e. with no unique origin) virtual image.
back
2 comments
Saying GNU Smalltalk "is not running in a virtual image" is incorrect.
For example, GNU Smalltalk does not load the whole standard library from scratch when you start it, the way for example Python does when you "import os". In addition it's perfectly possible (or even common) to load more packages into the image so that any file-based scripts you launch load faster.
And even though by default the compiler is written in C, if you load the "Compiler" package then GNU Smalltalk switches on the fly to a parser and bytecode compiler that's written in Smalltalk. If you load the "Debugger" package, exceptions will take you to a gdb-like debugger, with a companion text-based interactive inspector. (The scheduler is part of the image in the same way as in Smalltalk-80, and features such as exception handling and the debugger are entirely implemented in Smalltalk; the only custom feature of the GNU Smalltalk VM that the debugger uses is single-stepping).
So even though the image is not as pervasive as in Smalltalk 80 or Pharo (development happens in files and builds upon an image, instead of happening straight in the image), the image is there and it's not just an implementation detail.
Thanks for the explanation. It's about the wording. The fellow used "whole environment" and "image based development". I used the term "virtual image" from the Bluebook to mean the same. The Bluebook says "Two major components of the Smalltalk-80 system can be distinguished: the virtual image and the virtual machine. 1. The virtual image consists of all of the objects in the system [...]". The important point here is "all of the objects", especially also the compiler. There is no Smalltalk language outside of a Smalltalk-80 virtual image. You cannot do anything in an original Bluebook system without running the virtual image. That's what the fellow referred to by "whole environment" and I by "running in a virtual image". In GNU Smalltalk you don't need to load an image (i.e. persisted Object Memory state) to do anything reasonable. There is a compiler and and interpreter, and being "file based" is known to be a core benefit proposition of GNU Smalltalk, isn't it?
> In GNU Smalltalk you don't need to load an image (i.e. persisted Object Memory state) to do anything reasonable.
True but the first thing the VM does if it does not give an image is create empty classes and load files that define those classes. Only then does it do whatever it was asked to do, so the ObjectMemory was not loaded from a persisted state but is effectively indistinguishable from one.
Once the image exists, the main difference between the GST file-based approach and the traditional Smalltalk-80 image-based development is that saving the image back is not "saving your work" but "preparing a cache" in which to load source files ephemerally. But that's just an additional possible use of the image that could be implemented in Squeak/Pharo as well, just like GST had class browser for development if you really wanted.
Thanks. As I said, it's just about the wording. In the matter we are talking about the same. My whole point was to demonstrate to the fellow that it is well possible to use the Smalltalk language without being forced to always use a "whole environment", and that the ST-80 virtual image approach also has disadvantages. Obviously you came to the same conclusion.
The guy you're replying to is the guy behind GNU Smalltalk.
So what? I also implemented a couple of Smalltalk VMs, see https://github.com/rochus-keller/Smalltalk or https://github.com/rochus-keller/som, and I also spent a lot of time with the GNU ST implementation.
So what? So maybe you should listen to what they say about GNU Smalltalk. They might know a few things.
This is a discussion based on provable facts. Science needs no proof of authority.