Andrew Kesterson
8077806598
2.0.0 makes the error pool and the status registry thread safe, and it is an ABI break carrying the soname to libakerror.so.2. The break is a quiet one: __akerr_last_ignored became thread-local and akerr_next_error() now returns a context that already holds a reference, so objects compiled against a 1.x header and linked against 2.x count every reference twice and never give a slot back. Nothing about that fails to link, which is exactly what a guard is for -- include/akbasic/error.h feature-tests AKERR_THREAD_SAFE instead of AKERR_FIRST_CONSUMER_STATUS, which 2.0.0 also still defines and which therefore no longer distinguishes anything. 2.0.1 is the release this band needed most. The default unhandled-error handler ended in exit(errctx->status), and a process exit status is one byte: AKBASIC_ERR_BASE is 512, and 512 truncates to 0, so an unhandled AKBASIC_ERR_SYNTAX reported success to anything watching $?. Every other code in the band came out as some unrelated error's number. akerr_exit() substitutes 125 for anything a byte cannot carry, and a probe raising AKBASIC_ERR_DEVICE through FINISH_NORETURN now exits 125 rather than 7. It was latent here rather than live -- src/main.c handles the context and returns EXIT_FAILURE, and every test with a top-level ATTEMPT carries a HANDLE_DEFAULT -- but "no caller relies on it today" is not a property a header can keep true. tests/version_check.c asserts the mapping and fails if AKBASIC_ERR_BASE ever stops truncating to zero, because that is the day this stops being about our base. Chapter 10 gains a threading section: libakerror is safe from any thread now, and this interpreter is not and has no lock anywhere in it. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The akbasic guide
akbasic is a BASIC interpreter in the style of Commodore BASIC 7.0 — the dialect the C128 shipped with — and Dartmouth BASIC. It runs programs from a file or from an interactive prompt, and it is also a C library you can link into a game so that players can script it.
These chapters follow the shape of the C128 Programmer's Reference Guide: the language first, then each hardware area, then the reference sections. If you know BASIC 7.0 you can skip to Chapter 13, which is the list of everything that behaves differently here and why. Chapter 14 is the odd one out: it is about the interpreter rather than the language, for anyone embedding it, debugging it or changing it.
Chapters
| 1. Introduction | What akbasic is, what it is not, and how to build it |
| 2. Getting started | The prompt, your first program, saving and loading |
| 3. The language | Variables, types, arrays, operators, expressions |
| 4. Control flow | IF, FOR, DO, GOSUB, labels, ON, error trapping |
| 5. Strings and formatting | String functions, PRINT USING, PUDEF |
| 6. Graphics | GRAPHIC, DRAW, BOX, CIRCLE, PAINT, shapes |
| 7. Sound | SOUND, PLAY, ENVELOPE, VOL, TEMPO |
| 8. Sprites | SPRITE, SPRSAV, MOVSPR, collision |
| 9. Files and disk | Channels, DOPEN, program storage |
| 10. Embedding | Driving the interpreter from C |
| 11. Verb reference | Every statement, alphabetically |
| 12. Function reference | Every function, alphabetically |
| 13. Differences from BASIC 7.0 | What a C128 programmer needs to know |
| 14. Architecture | How the interpreter is put together, how to debug it, how to change it |
| 15. Error codes | Appendix: every value ER# can hold and every error line the interpreter prints |
The shortest possible start
$ cmake -S . -B build && cmake --build build
$ ./build/basic
10 FOR I# = 1 TO 5
20 PRINT "HELLO " + I#
30 NEXT I#
RUN
HELLO 1
HELLO 2
HELLO 3
HELLO 4
HELLO 5
READY
Two things in that program are not Commodore BASIC and will catch you out
immediately: variables carry a type suffix (I# is an integer) and +
concatenates a string with a number. Chapter 3 explains both.
Every example in these chapters is executed by the test suite and its output
compared byte for byte — see MAINTENANCE.md if you are editing them.