New C++ API

[myrrc]

Add new C++ API code.
Tests and examples will be added in the next PR

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 1698 untouched benchmarks
⏩ 9 skipped benchmarks¹

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_{Comparing myrrc/cxx2-code (b4aec09) with develop (5abaf98)}

Footnotes

1. 9 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[joseph-isaacs]

Please can we add the tests along side the code.

[0ax1]

noexcept audit

Given that this was already inconsistent I'd still vote for fully dropping noexcept.

Scope and criterion

This audit covers the new lang/cpp API.

noexcept is a public contract: adding it turns a propagated exception into
std::terminate. A Rust panic crossing an extern "C-unwind" function is not
a safe basis for marking a C++ function non-throwing.

There are a few clear omissions, but most apparent accessor candidates should
remain unannotated until the FFI guarantees no panic or unwind.

Clear noexcept additions

These do not allocate, do not use an FFI error path, and do not depend on an
unwinding FFI call.

Location	Candidate
lang/cpp/include/vortex/common.hpp:18 / src/f16.cpp:12	float16_t::operator float() const noexcept
lang/cpp/include/vortex/common.hpp:50	detail::to_ptype<T>() noexcept
lang/cpp/include/vortex/estimate.hpp:21	explicit Estimate(vx_estimate raw) noexcept
lang/cpp/include/vortex/array.hpp:144 / src/array.cpp:191	Array::nullable() const noexcept
lang/cpp/include/vortex/scan.hpp:36	PullRange::iterator::operator*() const noexcept
lang/cpp/include/vortex/scan.hpp:46	PullRange::iterator::operator==(std::default_sentinel_t) const noexcept
lang/cpp/include/vortex/scan.hpp:55	PullRange(Source&) noexcept
lang/cpp/include/vortex/scan.hpp:60	PullRange::end() noexcept
lang/cpp/include/vortex/scan.hpp:112	Partition::batches() & noexcept
lang/cpp/include/vortex/scan.hpp:223	Scan::partitions() & noexcept

For PullRange's default iterator constructor, noexcept is also appropriate.
Its constructor taking std::optional<Item> can be conditional:

iterator(Source* src, std::optional<Item> first)
    noexcept(std::is_nothrow_move_constructible_v<std::optional<Item>>);

The private raw-handle adopting constructors are also safe to annotate, for
consistency:

• Array(const vx_array*)
• DataType(const vx_dtype*)
• Expression(const vx_expression*)
• Scalar(vx_scalar*)
• Writer(vx_array_sink*)
• DataSource(const vx_data_source*, Session)
• Partition(vx_partition*, Session)
• ArrowStream(Session, ArrowArrayStream)
• all four view constructors

Scan(vx_scan*, Estimate, Session) is the exception: it uses
std::make_unique<std::mutex>(), so it can allocate and must remain potentially
throwing.

Candidates that need an FFI contract decision first

These are non-allocating in the current implementation, but call Rust functions
declared extern "C-unwind":

• Array::is_primitive(PType) const
• Scalar::is_null() const
• Validity copy constructor and copy assignment

They could become noexcept only if the FFI contract explicitly guarantees that
valid wrapper inputs cannot panic or unwind. Otherwise, leave them
unannotated.

Things that look like accessors but should not be noexcept

Function	Why
Array::size()	vx_array_len dereferences through a panic-on-null FFI helper; a moved-from Array has a null handle.
Array::has_dtype()	A valid internal Union or Variant dtype can panic while converting to the FFI dtype variant.
DataType::variant()	Same Union/Variant conversion panic path.
DataType::nullable()	Uses a panic-on-null FFI helper on a moved-from object.
DataSource::row_count()	FFI dereferences a null handle and dispatches through a data-source trait.
DataType::primitive_type()	Panics for non-primitive dtypes.
decimal_precision() / decimal_scale()	Panic for non-decimal dtypes.
fixed_size_list_size()	Panic for a non-fixed-size-list dtype.
PrimitiveView<bool>::value()	Panics on an out-of-bounds index.
Array::dtype(), DataSource::dtype(), Scalar::dtype()	Their FFI implementations allocate owning wrapper handles.
Copy constructors and assignments of owning wrapper types	FFI cloning allocates wrapper storage and moved-from values can produce null-handle panic paths.
dtype::*, scalar::of, expression constructors/operators	FFI allocation paths, and several have error or panic routes.
begin() / operator++() on PullRange	They call next() / next_partition(), which can throw VortexException.

The destructors written without noexcept, such as ~Validity(),
~ValidityBits(), and ~ArrowStream(), are already implicitly
noexcept(true) in this design. Adding the spelling would be documentation
only.

Recommendation

Make the high-confidence annotations now, but first fix the FFI panic paths
before treating the remaining accessors as no-fail. In particular, moved-from
wrapper behavior needs an explicit policy: either guard null handles and
return or throw normally, or document every non-move operation as invalid after
move. The former gives a much better basis for adding noexcept to simple
predicates and accessors.

[myrrc]

+1, I've removed noexcept everywhere except move constructors and free functions.

[0ax1]

Almost there! 🤝