Build.cachedir sat under TMPDIR, which dune makes private per run, so no
test run ever reused an object and every build in the suite was cold. It
moves to $XDG_CACHE_HOME/flan/objcache (FLAN_CACHE_DIR overrides), which
is safe because the keys are total: compile_c digests the source text,
the compiler's stamp and every flag; wasm_resource_dir digests the
builtins archive; compiler_object digests flan.cmxa and flan.a. Writes
were already .tmp-then-rename, so concurrent dune jobs are fine.
Macro.key was the one key that was not total -- prelude text plus the
call's forms, and nothing about the compiler whose codegen produced the
.so it names, which is dlopened straight back into this binary. Under a
per-run TMPDIR that never showed; under a durable cache it is a stale
expander that crashes rather than a compile error. It carries the
compiler's stamp now, handed across start_merged's exec in
FLAN_COMPILER_STAMP because a merged dev binary lives at a per-session
path and keying on that rebuilt a macro module every dev start.
Measured on dev-repl.flan, launch to bound socket: 2.0s cold against
0.48s warm. Whole-program flan build: 1.44s against 0.06s. Full dune
test 25.7s/30.1s before, 24.0s after, user CPU ~50s down to ~34s.
And the await: one timer covered two waits, a build then a bind, so
'the daemon never listened' was a wrong diagnosis of a build that had
not finished. listening now polls the process alongside the socket and
says which -- exited with a status, or still running and therefore still
building. A daemon that dies fails in milliseconds instead of costing
the whole timeout. Thirty seconds, down from a minute, because the build
it waits on is warm now.
Joseph Ferano
cdcdd70c4e