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

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# 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`.
```bash
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
```bash
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:
```bash
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
```bash
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:
```bash
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.
```bash
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.