The watch accumulator clears a slot lazily, on its next sample, and the reader
never compares epochs. A previous lane read that as a defect and left
watch_render_num's n=0 arm behind as dead code against the day the reader
became epoch-aware.
It should not. A stopped program takes no samples, so an epoch-aware reader
would report every slot as empty for as long as the program sat in a break
loop — and reading the numbers from the moment you stopped is the whole point
of stopping. The lazy clear is the right answer there.
What was wrong was narrower and lives in the editor: flan-watch--tick sent
`:reset t` five times a second at a program that could not answer it. The read
still goes out every tick; only the reset field drops, guarded on
flan-dev--stopped, which flan-dev.el's background poll already keeps current.
The n=0 arm is deleted rather than commented, since the only way to reach it is
the epoch check just rejected and dead code is an invitation to add one. n is
at least 1 whenever watch_render_num runs, so sum/n cannot divide by zero.
test-flan-watch.el asserts both halves with no daemon: a running tick carries
:reset, a stopped one does not, both still read the table and both leave a
reply in flight. Verified by mutation. What it cannot reach is the daemon
honouring the absent field; test_dev.ml drives a real program for that.
`flan-watch-ghost-call-regexp' allowed one hyphenated segment until this
lane's sibling widened it, so `watch-num-i64' matched as far as
`watch-num', required whitespace, found `-i64' and backtracked to
failure: the row appeared in the watch buffer as usual and the call site
got no inline value at all. Nothing automated covered the widening. It
does now — a block pinning both accumulator heads beside the four
one-segment ones, verified by putting the `?' back and watching exactly
those two checks fail.
The other half of that handoff asked for a test of `watch_render_num''s
`n=0' branch. It cannot be written: `s->num' is set in one place,
`watch_record', which always falls through to `s->n += 1', and the clear
and the increment sit inside one odd-generation window. The reader
never compares the slot's epoch to the global one, so a reset does not
make a slot read as empty either. The branch is dead, and the live
consequence is that a read taken after `:reset t' and before the
program's next sample reports the previous window — which is why the
existing test waits for the count to drop rather than reading once.
Recorded in HANDOFF-f3.md with the two ways out, both of which belong to
whoever owns runtime/flan_dev.c.
flan-watch-ghost-mode paints each watched value inline, after the line holding
the call that wrote it. An addition to the watch buffer and not a replacement:
both can be on at once, and turning either off leaves the other running.
The earlier note said ghost text was gated on a (watch ...) form in check.ml,
because nothing in the table carries a source location. That is true of the
table and the conclusion did not follow. The call site is in the buffer, and
the name in the table is the string literal in it, so the anchor is searched
for rather than reported. Nothing new is asked of the daemon. The head of the
call is a defcustom regexp, because watch-i64 is a name the program's author
chose in their own declare-c and only the C symbol behind it is fixed.
Both pictures are painted from one reply in flan-watch--absorb, so they cannot
disagree and there is no second watch request in flight. That meant the watch
buffer could no longer be the subscription: arming and the timer now hang off
flan-watch--consumers, and only the last consumer out disarms the table.
Overlays are replaced wholesale on every repaint rather than followed through
edits, which is the whole answer to invalidating one whose line moved. Only
buffers shown in a window are scanned.
Settled and written down: two sites of one name both show it and say so,
because the table has one slot and the last writer wins; a watch in a loop
shows the last value written, as the buffer does, because every better answer
is the query UI this design exists to avoid; a stopped program's values say
"last frame" and change face, since inline they sit in code that looks live;
a site with no row is annotated only when the table reports overflow.
syntax-ppss moves point and clobbers the match data, so calling it inside a
re-search-forward loop and then reading match-string restarts the scan and the
loop never ends. Everything is read out before the check now.
emacs/test-flan-watch.el covers it, loaded from test-flan-cider.el the way
test-flan-mode.el is, so no build change is needed. 203 checks, 0 failures.
