An archival fork of Public Domain Smalltalk (PDST), slightly updated and optionally integrated with HAL/L2 (sold separately) (link dead, product defunct, contact me for more info). The hooks which were added to integrate with my old osdev project may be useful for embedding in other applications though. I also (hopefully) have on a disc somewhere some other variations of this codebase with more extensive changes and better embedding, as well most of an implementation in Java, if anybody is interested (note that none of this is maintained or finished though!).
Public Domain Smalltalk wasn't originally developed by me. It's mostly the work of Douglas E. Hammond and Timothy Budd. Of course, the most credit goes to Alan Kay, the original developer of the Smalltalk language and teacher of Object-Oriented Programming.
You understand and agree that this material is entirely in the public domain, that it is made available to you without charge and that it will only be used based on the express disclaimer by Douglas E. Hammond and all other persons or organizations participating in its production, storage and transmission of any warranty or guarantee, express or implied, of any aspect of this material itself and of any results that may be obtained from its use.
The original code is archived under "pdst" in the Little Smalltalk archives:
https://github.com/kyle-github/littlesmalltalk/tree/master/archive
I'd recommend Timothy Budd's book "A Little Smalltalk", although it's quite dated now (as are most Smalltalk resources). Public Domain Smalltalk is essentially a clone of Little Smalltalk (the main difference being support for proper garbage collection).
Inline function syntax has been fixed (modern compilers take issue with functions which are marked inline but not marked static).
Support for underscores in class/method names has been added with an optional ctype hack. The higher-level compiler (in BaseLibrary.smalltalk) now allows underscores by default.
Basic support for embedding PDST in an application has also been added (the L2_SMALLTALK_EMBEDDED flag will rename the main function to L2_SMALLTALK_MAIN, so it can be invoked from an external main function). Replacement ctype functions have also been added as preprocessor macros, and these are also enabled by the L2_SMALLTALK_EMBEDDED flag (although you might want to remove these if you're using a stable libc - the system this was embedded in only has a partial libc, so this was just a hack).
Only the virtual machine and standard library are included here. The tests, documentation and build scripts from the original (see link above) should still be relevant.
(This is coming from a larger private repository, where Smalltalk has been integrated into an operating system, so the original tests and build scripts didn't entirely make sense in this context.)
To compile:
gcc pdst.c -opdst -lm
(Using -dL2_SMALLTALK_UNDERSCORES will enable underscores in class/method names. Using -dL2_SMALLTALK_EMBEDDED will enable built-in ctype functions and rename main to L2_SMALLTALK_MAIN.)
To create an initial snapshot:
./pdst -c BaseLibrary.smalltalk
To continue running an existing snapshot:
./pdst -w snapshot