Ecosystem gate — building real-world C with kit

This suite proves kit can compile, archive, link, and run real upstream C projects, and that the results match a reference clang build byte-for-byte.

It is intentionally a differential, reproducible gate:

• Reproducible — sources are pinned upstream releases (URL + sha256) fetched into the kit cache dir, never vendored into the repo. Provision once with network access; the gate then runs fully offline against the cache.
• Real usage — each project is built the way it is actually consumed: every translation unit is compiled with kit cc, archived into a static library with kit ar, and a driver (the project's own shell/interpreter, or a small use/<name>.c) is linked against it and executed.
• Differential — the program's deterministic output is asserted two ways: against a checked-in golden (expected/<name>.txt) and against the same program built with the host clang (the differential oracle).
• Both opt levels — every project runs at -O0 and -O1.

Run it

make provision-ecosystem      # fetch + verify + extract pinned sources (network)
make test-ecosystem           # build with kit + clang, run, diff (offline)

Or directly, with finer control:

scripts/ecosystem.sh status                 # what's provisioned
scripts/ecosystem.sh fetch sqlite           # fetch one project
test/ecosystem/run.sh sqlite lua            # run only these
KIT_TEST_OPTS=O0 test/ecosystem/run.sh      # one opt level
test/ecosystem/run.sh --update              # refresh goldens (from clang)

Projects

project	what the driver exercises
sqlite	shell built from the amalgamation runs SQL: joins, aggregates, CTEs, window functions, JSON
lua	~30-TU static lib + interpreter runs a script: GC, closures, coroutines, string.format, integer/float
cJSON	parse / navigate / build / serialize JSON
lz4	block compress/decompress round-trips
miniz	deflate/inflate round-trips + CRC-32 / Adler-32
tinyexpr	expression compile + variable binding
yyjson	read / navigate / mutate / write JSON

Adding a project

Drop a recipes/<name>.recipe (contract documented in recipes/sqlite.recipe): pin ECO_URL + ECO_SHA256, point ECO_SRCDIR at the source root, define eco_lib_srcs and eco_run, and add a driver under use/ if the project has no suitable main. Then scripts/ecosystem.sh fetch <name> and test/ecosystem/run.sh --update <name> to seed the golden.

Known bugs (kept red on purpose)

Failures are not xfailed or worked around — see known_bugs/. The gate stays red until they are fixed, and each failing build's artifacts are preserved under build/ecosystem-fail/ for investigation.