The writer is the game thread, in every allocation and every free; the reader
is the agent's listener, on a program that is running. Nothing stood between
them. The consequence is not a slightly wrong count: a row's type pointer and
its length mean nothing apart, and a reader that takes the new pointer with the
old length reads off the end of a string literal.
Each entry now carries the watch table's seqlock, odd while it is written, and
a reader copies the entry and re-reads the counter before believing it. The
compaction bumps a table-wide counter around itself, because it moves entries
between slots and no per-slot counter can describe that; a scan that sees that
counter move walks again. It clears the table slot by slot rather than with one
memset, since the memset would zero the counters a reader was holding.
The breakdown and the leak report stay answerable while the program runs, which
is the moment they are for. reg at does not: whether one address is still live
is exactly what a running program is changing, so it is refused the way every
break verb is refused, which is what the daemon already did on its own side.
Joseph Ferano
9d10e7edb0