pthread bindings with darwin opaque sizes (mutex 64B, cond 48B; glibc
divergence is a C3 per-OS item). Mutex/Cond initialize IN PLACE and
Pool lives behind Pool.create's heap pointer — POSIX sync objects are
address-sensitive, so nothing here moves after setup. Thread.spawn
takes the C2 re-entry contract entry (callconv(.c), fabricates its own
Context); Pool workers do exactly that with a per-worker malloc-backed
GPA, then run default-conv tasks inside it. submit returns false on a
full backlog (httpz thread_pool backpressure); shutdown finishes
queued work and joins every worker.
examples/1637 pins: 4 raw threads x 1000 locked increments, 100 pool
tasks summing exactly once across 4 workers, a held worker + full
backlog refusing the next submit, clean shutdown. JIT + AOT (AOT run
three times). The std.sx barrel carries thread; .ir snapshot regen is
the usual renumbering.
Both halves of the C2 contract already work in JIT and AOT; these
examples pin them. 1635: libc qsort drives an sx callconv(.c)
comparator passed by name as a typed fn-pointer param. 1636: a real
pthread enters sx through a callconv(.c) entry, fabricates its own
Context (push Context with a local GPA), and runs default-conv sx code
that allocates through it — the re-entry contract std.thread (S6)
stands on. Also unblocks the sqlite callback APIs (hooks/UDFs) left
unbound by design in P5.1.
