[BUG?] Very strange behavior, execution of a function is interrupted

[Sebastian Gniazdowski <sgniazdowski@gmail.com>]

Hello,
it's quite a lost game to explain this, but I'll try:

- there is a scheduler called from sched +1 and once from zle -F
- it detects timed-out tasks, moves them to ZPLG_RUN, then executes
them reading them from this array

Problem: sometimes execution never reaches this line and beyond:
https://github.com/zdharma/zplugin/blob/7a24478e5862a1359b6cfb2887a792213be07e3a/zplugin.zsh#L1485

Some cycles of the preceding loop are then also skipped.

I feel very helpless in explaining this, maybe there's standard
questions sheet for situation where bug in exec.c is suspected?

I know `break 2' inside a function will break out of loop that
contains the function call. But I don't know what could exit a
function. I have debug prints and observe this clearly. At the
mentioned line, no execution occurs, ZPLG_RUN isn't cleared, I get to
run some tasks twice.

Twice when I checked, it was happening when zle -F was called so near
next second, that timeout'd tasks detection included two time slots:
"0" (0 seconds after first precmd, handled by zle -F) and "1" (1
second after first precmd, handled by sched +1).
-- 
Sebastian Gniazdowski
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