Joseph Ferano
0c523cfe8b
You run a program under flan dev, it opens a raylib window, you close the window, main returns — and there is no way to get another window short of flan-dev-restart-program, which throws away the build, the session and every global with it. In Common Lisp or Clojure the image outlives main, so you call it again. The process here already outlived main: the exit hook flushed, closed stdout and sat in for (;;) pause(). Nothing could wake it. So main() is a loop. The hook records the status and longjmps back into a setjmp in main() — there is no return available, since flan_exit is reached from wherever the program happened to be — and the thread waits on a condition variable until the new rerun op signals it. The main thread is the one that runs main again: a window belongs to the thread that opened it, and on macOS to the first thread of the process. A longjmp pops no frame, so the park first empties the handler stack, the restart stack and the shadow frame chain, each of which was a chain of allocas in stack the next run is about to write over. Nothing else is reset; the second run reads whatever the first left in the globals, which is the semantics that was asked for. Closing stdout had to go with it. That was how the compiler learned the program was done, but a pipe delivers EOF once, so the signal and the program's output were the same resource and spending it left the second run with nowhere to print. The descriptor hazard the old code reopened /dev/null for goes away with the close that caused it. Liveness is asked for instead, through a weak symbol in the same style as the agent's, and is now three states rather than two: Live, Parked and Gone. Every guard branches on that before consulting the break state, because the agent's listener answers "running" while the program is parked and telling somebody whose program has finished that it is running is worse than saying nothing. Only eval accepts a parked program — it queues and waits for nothing, and the queued module installs at the first frame boundary of the next run, so a body can be fixed while parked and the re-run executes it. Everything else needs a frame boundary or a stopped stack, has neither, and says which, naming the command that gets the program back. A re-run while the program is running is refused rather than queued: the test and the signal happen under one mutex, so two mains writing the same globals at once never starts. :parked rides on every reply beside :stopped, for the reason :stopped does — finishing is as unannounced as stopping, more so when the way it happens is a mouse click on a title bar. Emacs shows flan:parked in the modeline and binds flan-rerun to C-c C-M-x.
What is in here, and what is still true
These are the documents that are written once and read occasionally: the reasons behind the code, the
reports from finished investigations, and the record of individual work sessions. The documents that are
edited every day stay at the repository root, because source comments cite them by bare filename from
dozens of places and a path that moves is a path that rots. So plan.org, NEXT.md, spec-memory.md
and spec-conditions.md are one directory up, and everything here points back at them.
A note on how to read the citations below: a document in this directory that says plan.org means the
one at the repository root. Nothing in docs/ is named for a file at the root, so there is no ambiguity,
and rewriting a hundred prose mentions into ../plan.org would have cost more in readability than it
bought in precision.
If you have thirty seconds
Read BUILT.md. It is by far the largest document here and it is the one that pays: it holds the
reason behind every part of the compiler that exists, from why nothing is ever dlclosed to why the
printer is a compile-time walk over a type rather than a runtime function. It is current, it is
maintained, and deleting it would mean deriving all of it again. If you want to know why a thing is the
shape it is, the answer is in here.
After that, ../NEXT.md at the root for what is actually in flight, and REFERENCES.md here for
where the evidence comes from — the reference clones on this machine, what each one answers, and the
standing rule that a claim in these notes was read out of a clone rather than recalled.
The current documents
| File | What it is |
|---|---|
BUILT.md |
Why the parts that exist are shaped the way they are. The longest and the most load-bearing document in the repository. Current. |
DISCUSS.md |
Open questions, raised and deliberately not answered. Nothing in it is a decision or a task; entries that have since been answered say so and point at where the answer landed. Current, though it is half archive by now. |
PORTING.md |
What the author's game, siam-farmer, needs from Flan that Flan does not have yet, measured against the code that exists rather than against a plan. It is the requirements document the language is actually steering by. Current. |
REFERENCES.md |
The reference clones under ~/Repositories, what each one is consulted for, and the specific files and lines already cited from them. Current. |
The reports
| File | What it is |
|---|---|
SPIKE-GENERICS.md |
Milestone 5's parametric polymorphism, run early and out of order as a spike. The spike succeeded and generics landed, so this is the report of finished work rather than a live plan — but its findings about where the cost falls are still the reason the implementation looks the way it does. Historical, findings still stand. |
overview.md |
The first brainstorm, from before the language had S-expressions. It says in its own first line that it is superseded and no longer accurate. Kept for history only; its table of what changed is the only part worth reading. Superseded. |
handoffs/
One report per work session, each written by whoever held the branch at the time. They are the
operational record: what was attempted, what was measured, what was decided without being able to ask,
and what was left open for the next lane. They are all historical the moment they are written — a handoff
describes a session that has ended — but they are cited by name from source comments and from NEXT.md,
because the reasoning behind a guard or a calling convention is often only written down once and this is
where it was written.
Six of them are the hand-written x86-64 backend, read in the order the work happened:
handoffs/HANDOFF-x86-rt.md set the remaining-items list that the four after it close, handoffs/HANDOFF-x86-redef.md
built the redefinition emitter, handoffs/HANDOFF-x86-aggregates.md took that across the struct boundary,
handoffs/HANDOFF-x86-guards.md settled the two guards nothing reaches, handoffs/HANDOFF-x86-debug.md added debug
information, and handoffs/HANDOFF-x86-cost.md measured what the backend costs and set the survey running on its
own so a refusal cannot sit unnoticed again.
The other six sessions are unrelated to each other. handoffs/HANDOFF-arith.md is why a divide by zero is a condition
rather than a SIGFPE. handoffs/HANDOFF-raylib-ports.md is the running record of the last two raylib example
ports, whose lasting findings were folded into PORTING.md, and handoffs/HANDOFF-cimport-ptr.md is the arm
cimport.ml's header check had been promising in a comment and not implementing — which is what those two ports
found, worked around and wrote up. handoffs/HANDOFF-devtest-noise.md is the linker
error dune test used to print on every run. handoffs/HANDOFF-emacs-flake.md is the test_emacs flake that
turned out to be SIGPIPE killing the daemon mid-reply, and it is worth reading for the two mechanisms it
rules out as much as for the one it found. handoffs/HANDOFF-tidy.md is this reorganisation.