# Known Issues

Bugs found during development or downstream use, tracked here because this
repository's issue tracker is disabled. One entry per bug; when an entry is
fixed, record the fix in `CHANGELOG.md` and update its status here rather than
deleting it.

---

## Compound datatype message version 5 is not parsed (HDF5 2.0)

**Status:** fixed on `main` in `a13ff51` (2026-06-03); **not in the v2.1.0
tag**, which was cut five commits earlier. Ships in the next release.

**Reported by:** M. Scot Breitenfeld (The HDF Group), 2026-09-08, against v2.1.0.

**Summary:** `clawhdf5-format` v2.1.0 rejects any dataset with a compound
(struct) datatype written by an HDF5 2.0 library in `libver='latest'` mode:
`InvalidDatatypeVersion { class: 6, version: 5 }`.

**Reproduction** (h5py 3.16.0 / HDF5 2.0.0):

```python
import h5py, numpy as np
dt = np.dtype([('x', 'f8'), ('y', 'f8'), ('id', 'i4')])
data = np.array([(1.0, 2.0, 10), (3.0, 4.0, 20)], dtype=dt)
f = h5py.File('compound.h5', 'w', libver='latest')
f.create_dataset('particles', data=data)
f.close()
```

Committed as `crates/clawhdf5-format/tests/writer_h5py_tests.rs::read_h5py_generated_compound`
(`#[ignore]`d; needs `python3` with h5py on `PATH`). Run with
`cargo test -p clawhdf5-format --test writer_h5py_tests -- --include-ignored`:
v2.1.0 gives 25 passed / 1 failed; `main` passes everything.

**Root cause:** the compound (class 6) branch of `Datatype::parse`
(`crates/clawhdf5-format/src/datatype.rs`) accepted only versions 1–4. Datatype
message versions 4 and 5 changed only the Reference and Complex classes, so a
v5-tagged compound uses the unchanged v3 member-list layout.

**Fix:** versions 3–5 are accepted for compound (class 6) and array (class 10)
datatypes, and data layout message version 5 is accepted too (needed for every
chunked dataset written by HDF5 2.0). Byte-level regression tests:
`test_compound_v5_from_hdf5_2_0`, `test_array_v5_from_hdf5_2_0`.

## Native complex datatype (class 11) is mis-parsed (HDF5 2.0)

**Status:** fixed 2026-09-18. Found while validating the report above.

**Summary:** HDF5 2.0 native complex types (`H5T_COMPLEX_IEEE_F64LE` etc.)
were parsed as if they carried a compound-style member list. The properties are
actually a single base floating-point datatype, so the parser produced a garbage
datatype, or `UnexpectedEof` when the complex type was a compound member. h5py's
default numpy-complex mapping is unaffected (it writes a `{r, i}` compound);
only files using the native type through the C API / h5py low-level API hit this.

**Fix:** class 11 parses its base type and is surfaced as the equivalent
`{r, i}` compound. Tests: `test_complex_v5_from_hdf5_2_0`,
`test_compound_with_complex_member_from_hdf5_2_0`,
`writer_h5py_tests.rs::read_h5py_generated_native_complex`.

## Revised reference datatype (class 7, version 4) is not parsed

**Status:** open, unconfirmed against a real file.

**Summary:** HDF5 1.12+ `H5T_STD_REF` references use datatype version 4 with
reference types 2–4 (object2 / region2 / attribute), which `Datatype::parse`
rejects with `InvalidReferenceType`. h5py still writes the legacy v1
object/region references, which read correctly, so no reproducing file has been
generated yet; one written with the C API (`H5T_STD_REF`) is needed.

## `clawhdf5-gpu` `gpu_tests` can hang under the default parallel test runner

**Status:** open. Observed 2026-09-18 (RTX 5060 Ti, Linux).

**Summary:** during `cargo test --workspace`, the `gpu_tests` binary sat idle
(~1% CPU) for 25+ minutes and had to be killed. Run single-threaded it passes
in seconds (20/20): `cargo test -p clawhdf5-gpu --test gpu_tests -- --test-threads=1`.
Suspected cause: several tests creating wgpu devices concurrently (possibly
compounded by the rest of the workspace's tests loading the machine). Not yet
root-caused; workaround is `--test-threads=1` for that crate.