Six refusals in the runtime called _exit(134) where every other error had
learned to park: no restart by that name, a restart taken with the wrong
arguments or with none, a defer that invoked one, a null allocator, and
free-all on something with no region. Under a merged flan dev the compiler is
in that process, so a program that named a restart nobody established took the
session down with it, which is the one thing the break loop exists to prevent.
They park now. Not through flan_break_hook, which is what bounds and
arithmetic use: that hook may answer by aiming a transfer channel, and these
six are called by emitted code that falls off the end with no channel anywhere
in the call, so a restart chosen against one would be accepted and dropped.
flan_trap_hook says the other thing instead — stop here, let everything be
read, and refuse the resume with a reason.
All six park, for two reasons rather than one. Four are guards that fire
before the operation they guard, so nothing is half done and the frame reads
like any other. The other two fire mid-transfer, with the frame's defers
possibly half run, and they park only to be looked at: stopping on a torn
unwind is strictly more than exiting before anyone can ask what tore it.
The break loop grew a per-snapshot resumable flag for it. Restarts are still
listed and still numbered, the terminal marks them untakeable and the socket
reports the same positions as unreachable, and the listener refuses a choice
with the trap's own sentence rather than the thunk-boundary one.
Standalone builds die exactly as they did: nothing installs the hook in a
program that did not import the agent, and the acceptance case for free-all
still wants exit 134 and the same message.
The review entry that asked for this named flan_exit_hook, which is normal
termination and not this at all; it is struck out with the correction.
