Phase 0 last β-shape site. Two concerns in one commit because the
refactor surfaced the rename:
- selfhost/cmd/wcc/cgen.ww cgout buffer (cgoutbuf/cap/len + arena +
cgout_grow + CGOUT_INIT_CAP) → memio.state + io.stream behind a
one-shot lazy-init guard. cgout_enable drops its *arena param;
memio.reset in cgout_flush keeps the buffer sticky across fns so
the arena's amortisation survives — re-init per fn would abandon
the buffer and re-grow from 0 via the 8→…→65536 ladder for every
function (no io.close path → no os.free).
- lib/memio/memio.ww private fn grow → dynamicgrow. Symmetric with
dynamicwrite / dynamicclose; required because cstage bundles all
imported modules into a flat TU and resolves private fns by
unqualified name, so the new `import memio;` in wcc's bundle
collided with selfhost/cmd/wcc/mem.ww's arena `grow`. Module-aware
private-fn scoping in cstage is task #9.
@test fn dynamicgrow in memiotest.ww (same package as memio.ww)
renamed to dynamicgrowcases to free the name; new suffix mirrors the
file's existing fixedwritecases / borrowedreadcases convention.
Lazy-init guard cgoutinit. memio.dynamic runs once on first
cgout_enable; subsequent enables just set cgoutmode. Mirrors
lib/log/log.ww:124 ensureinit. Without it, ~14 mmap syscalls per fn
and ~100 MiB+ cumulative leak on a typical bootstrap.
io.write bare discard in emitbytes mirrors lib/log/log.ww:169 —
memio.dynamicwrite never returns io.closed (memio.ww:166).
Verified 132/132 incl. 995_self_rebuild byte-identity.