Environment variables

Every OCJS_* env var the build system honours — exceptions, SIMD, BigInt, EVAL_CTORS, LTO, strict types.

The build system reads these env vars before compile and link. Set them on the command line, in CI, or in build-configs/configurations.json.

Compile-time flags

Variable	Default	Effect
`OCJS_EXCEPTIONS`	`1`	Compile every TU with `-fwasm-exceptions`. Mixed builds fail at link.
`OCJS_SIMD`	`1`	Compile every TU with `-msimd128` (baseline SIMD).
`OCJS_RELAXED_SIMD`	`0`	Additionally emit `-mrelaxed-simd`. Chrome/Firefox-only — breaks Safari.
`OCJS_BIGINT`	`1`	Compile with `-sWASM_BIGINT`. Saves ~30 KB JS glue.
`OCJS_EVAL_CTORS_LEVEL`	`2`	`-sEVAL_CTORS=N`. Levels: 0 off, 1 safe-side-effect, 2 full.
`OCJS_LTO`	`0`	Enable LLVM LTO. Smaller binary, ~3× slower build.
`OCJS_STRICT_TYPES`	`0` (warn-only)	When the link-time `.d.ts` post-processor rewrites method signatures to `unknown` (or codegen collects unbound-reference diagnostics), the build always prints a triage summary to stderr. Set `=1` to escalate that condition to a build failure.

Build orchestration

Variable	Default	Effect
`OCJS_CONFIG`	`single-threaded`	Named preset from `configurations.json`. Alternative to the `--config <name>` CLI flag — both end up at the same place.
`OCJS_PARALLEL_JOBS`	CPU count	Max parallel compile jobs.
`OCJS_CACHE_DIR`	`./cache`	Where to store cached `.o` files and bindgen output.
`OCJS_BUILD_DIR`	`./build`	Intermediate build outputs.
`OCJS_DIST_DIR`	`./dist`	Final wasm + JS + .d.ts artifacts.

Docker-specific

Variable	Default	Effect
`OCJS_DEPS_VERSION`	from `DEPS.json`	Override the dep pinning (OCCT, freetype, rapidjson).
`OCJS_EMSDK_DIR`	`/deps/emsdk`	Location of the emscripten SDK inside the image.
`OCJS_PYTHON`	`python3`	Python interpreter for the bindgen.
`OCJS_OUTPUT_DIR`	`/src` (in container) / `./dist` (host)	Where the link step writes the final `.wasm`, `.js`, `.d.ts`, and `.build-manifest.json`. In-container default is `/src` so the canonical single-mount Quickstart (`docker run -v "$(pwd):/src" …`) writes outputs next to the YAML automatically. Override to a separate path if you need outputs outside the bind-mount.

Diagnostics

Variable	Default	Effect
`OCJS_VERBOSE`	`0`	Print every compile / link command.
`OCJS_DUMP_CACHE_KEYS`	`0`	Print the cache-key contents on miss (debug spurious cache invalidation).

Worked example

# Custom-trimmed Os build for an embedded edge runtime.
# OCJS_STRICT_TYPES=1 escalates the missing-typedef warning to a build
# failure -- recommended in CI; omit it for local builds (warn-only is
# the default).
OCJS_CONFIG=single-threaded-smallest \
OCJS_STRICT_TYPES=1 \
OCJS_PARALLEL_JOBS=8 \
./build-wasm.sh link build-configs/edge-runtime.yml

Named compile-time configurations — named preset list.
Two-channel config model — compile-time vs link-time channels.

Compile-time flags

Build orchestration

Docker-specific

Diagnostics

Worked example

Related

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