Files
ocp/docs/building.md
stroblme 6139852768 Phase 10A/10B Inc 0: build system, handle model, first module surface
Builds n3xd-ocp end to end and publishes 7.9.3.1.dev1 to the Gitea registry,
where it installs anonymously and passes its suite.

- occt/Dockerfile: OCCT 7.9.3 compiled once into a manylinux_2_28 builder
  image (base digest + tarball sha256 pinned), Draw/VTK/Tk/Xlib/OpenGL off,
  FreeType on, -O2 without fast-math or march=native. A final layer asserts
  TKService/TKV3d exist with no libGL/libX11 DT_NEEDED, which is what lets the
  app image drop libgl1/libx11-6. Mounted into, never built FROM.
- scikit-build-core + nanobind STABLE_ABI -> one cp312-abi3 extension that
  registers every OCP.* submodule via PyImport_AddModule, so `import
  OCP.TopoDS` needs no shim and cls.__module__ is right. Version <occt>.N is
  asserted against the OCCT found, keeping occt_version() truthful.
- occt_handle.h: type caster for opencascade::handle<T> over OCCT's intrusive
  refcount. Wrappers are non-owning instances holding exactly one handle in
  their keep-alive list, reusing an existing wrapper so identity survives a
  round trip. Transient constructors go through ocp_new (never nb::init<>,
  which would let OCCT delete nanobind's storage); the caster refuses a
  refcount-0 object rather than corrupt the heap. Verified under ASAN with no
  memory-safety errors, plus an RSS bound over 50k create/destroy cycles.
- Sub-shapes are returned by value everywhere, making the TShape lifetime class
  that segfaulted a process-global face memo unrepresentable.
- Standard_Failure derives RuntimeError, with ~20 concrete types dispatched on
  the dynamic OCCT type (cad_pool marshals failures home by type name).
- Inc 0 surface: gp subset, TopAbs, TopoDS (+ downcasts), TopExp, TopLoc,
  TopTools, BRep, BinTools, Poly, Standard. 34 of the app's 139 symbols.
- n3xd_ocp: additive APIs kept out of the OCP namespace so parity testing stays
  meaningful. bintools (shape <-> bytes, GIL-free, byte-identical) and _debug.

Two findings worth the record, both verified against the stock wheel rather
than assumed: upstream binds __hash__ but leaves __eq__ at identity, which is
exactly what geom_memo.py's hash-bucket + IsSame scan is built around, so we
match it instead of "fixing" it; and BinTools can release the GIL after all, by
slurping the file-like object instead of bridging a streambuf that would call
back into Python.

Gate: BREP round-trips are byte-identical to cadquery-ocp-novtk across six
fixtures (the generator asserts stock idempotency first). That matters beyond
IPC — derive.py content-addresses BREP payloads by sha256 and stores the ref.
2026-08-10 16:10:28 +02:00

4.2 KiB

Building

Everything runs through make; make help lists the targets. All compilation happens inside the OCCT builder image, so the only host requirements are Docker and (for publishing) uv.

The builder image

occt/Dockerfile compiles OCCT 7.9.3 once inside quay.io/pypa/manylinux_2_28_x86_64 (both the base digest and the source tarball's sha256 are pinned) and installs it to /opt/occt.

make image        # ~40 min on 16 cores
make image-push   # needs: docker login git.stroblme.de

It is a compiler appliance: wheel builds mount the repo into it rather than FROM it, so iterating on the binding never re-layers the kernel. Add new packages at the end of the Dockerfile — earlier layers stay cached and the kernel is not recompiled.

The configuration turns Draw, VTK, Tk, Xlib, OpenGL and GLES off and FreeType on, and the last layer asserts the result: TKService and TKV3d exist (text emboss reaches Font_BRepFont through them), neither carries a libGL/libX11 DT_NEEDED, and freetype is linked. That is what lets the app image eventually drop libgl1 and libx11-6. Flags are -O2, no -ffast-math, no -march=native: OCCT's version is a determinism input for assay's goldens, so the binding must not introduce a different FP contract than the kernel it wraps.

Production never compiles OCCT. The host has 4 cores and make update is a git pull plus a compose build; the kernel arrives prebuilt inside the wheel, which is the whole reason this image exists.

Build cache

Object files, ccache, the pip cache and the build venv live under $(CACHE), default /mnt/cache/n3xd/ocp — off the root filesystem, which is tight on the dev box. Change it per invocation with make CACHE=/somewhere wheel, or reset it with make clean-cache.

The loop

make dev      # incremental compile + pytest — the inner loop, seconds
make test-asan # handle-model memory-safety check
make wheel    # full build: compile, stubs, repack, auditwheel, smoke test

make wheel compiles twice on purpose: stubs are produced by importing the freshly built extension, so they cannot exist before the first compile, and the wheel is packed from the source tree. The second pass is incremental.

The smoke test installs the repaired wheel into a bare venv and imports it with LD_LIBRARY_PATH unset — the only honest proof that auditwheel made it self-contained.

Fixtures

tests/data/*.brep are the byte-identity references and are generated under the stock wheel, from the app checkout:

cd ../app && .venv/bin/python ../ocp/tools/gen_fixtures.py

The generator asserts stock is idempotent for each fixture before recording its digest — otherwise the gate would compare against a moving target. Regenerate only when deliberately re-blessing (e.g. the OCCT 8.0 bump).

Publishing

make version   # confirm what you are about to publish
make publish   # uv publish -> https://git.stroblme.de/api/packages/N3XD/pypi

Credentials come from .secrets (gitignored) as UV_PUBLISH_USERNAME / UV_PUBLISH_PASSWORD; the username is a real Gitea username, not the PyPI __token__ convention, and the token needs package: Read and Write.

A version can never be republished. Iteration builds therefore carry a .devN suffix and are the only ones the registry's cleanup rule collects; bump N in pyproject.toml for each upload.

Consumers read anonymously — the N3XD org is public:

uv pip install --index-url https://git.stroblme.de/api/packages/N3XD/pypi/simple/ \
    --prerelease=allow n3xd-ocp

Gitea serves no root /simple/ listing (404), only the per-package path, which is all pip and uv ask for.

Parity

tools/parity_venv.sh builds a side environment where the app runs against this wheel instead of the stock one. The app's manifests are never edited: both distributions own the OCP/ import path and a process can hold only one OCCT build, so a swap is per-environment and reversible by re-syncing.

tools/parity_venv.sh           # from the registry
tools/parity_venv.sh --local   # from wheelhouse/
python tools/inventory.py --check

Coverage is expected to be partial until the increments land — --check prints what is still missing, grouped by module, which is the work queue.