Enforce base resource alignment limits

[bdice]

Description

Closes #2342.

Restores alignment enforcement for base CUDA memory resources by rejecting nonzero allocations whose requested alignment exceeds CUDA_ALLOCATION_ALIGNMENT. Zero-size allocations continue to return nullptr without validating the requested alignment.

Re-enables the previously disabled oversized-alignment tests for device_buffer, device_scalar, and device_uvector.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: f6174b63-97a2-4e89-871f-6690dcff2896

📥 Commits

Reviewing files that changed from the base of the PR and between 4c3816a and 746c176.

📒 Files selected for processing (1)

• cpp/src/mr/detail/cuda_async_managed_memory_resource_impl.cpp

🚧 Files skipped from review as they are similar to previous changes (1)

• cpp/src/mr/detail/cuda_async_managed_memory_resource_impl.cpp

---

📝 Walkthrough

Summary by CodeRabbit

• New Features

  • Added an alignment validation utility to check supported alignment values.
  • Allocations now respect the requested alignment when applicable.

• Bug Fixes

  • Memory resources now reject unsupported alignments before allocating.
  • Zero-byte allocation paths consistently return null without throwing.

• Tests

  • Re-enabled alignment tests to verify error handling and zero-size behavior.

Walkthrough

Adds a central predicate is_supported_base_resource_alignment() and enforces it in memory resource allocate methods, forwards alignment to pool allocators for async resources, short-circuits zero-byte allocations, and re-enables alignment-related tests.

Changes

Alignment Validation and Testing

Layer / File(s)	Summary
Alignment validation contract and implementation cpp/include/rmm/aligned.hpp, cpp/src/aligned.cpp	New is_supported_base_resource_alignment() declaration and definition; SPDX year update.
Base memory resource alignment enforcement cpp/include/rmm/mr/cuda_memory_resource.hpp, cpp/include/rmm/mr/managed_memory_resource.hpp, cpp/include/rmm/mr/pinned_host_memory_resource.hpp	Leaf memory resources add runtime alignment checks (using the new predicate) and return nullptr for zero-byte allocations where applicable; invalid alignment triggers rmm::bad_alloc.
Async and view memory resource alignment support cpp/include/rmm/mr/cuda_async_view_memory_resource.hpp, cpp/include/rmm/mr/system_memory_resource.hpp, cpp/src/mr/detail/cuda_async_managed_memory_resource_impl.cpp, cpp/src/mr/detail/cuda_async_memory_resource_impl.cpp	Remove [[maybe_unused]] on alignment parameters, validate alignment, and forward alignment to underlying pool allocators (async paths).
Alignment validation test coverage cpp/tests/device_buffer_tests.cu, cpp/tests/device_scalar_tests.cpp, cpp/tests/device_uvector_tests.cpp	Previously disabled large-alignment tests are enabled to assert rmm::bad_alloc for over-aligned requests; zero-sized buffer test wrapped in EXPECT_NO_THROW.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• rapidsai/rmm#2330: Introduces constructors that pass caller-requested alignment into memory resource allocate calls, which this PR's validation now enforces.
• rapidsai/rmm#2343: Also modifies allocation call paths to handle and forward alignment through adaptors/allocators.
• rapidsai/rmm#2337: Adjusts default device_buffer alignment handling to align with enforced validation constraints.

Suggested labels

bug, non-breaking

Suggested reviewers

• wence-

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 22.73% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Enforce base resource alignment limits' clearly and concisely describes the main change - restoring alignment enforcement for CUDA memory resources.
Description check	✅ Passed	The description is related to the changeset, explaining the restoration of alignment enforcement and re-enabling of tests, matching the implemented changes.
Linked Issues check	✅ Passed	The PR successfully addresses issue #2342 by enforcing alignment limits in base CUDA memory resources and re-enabling the previously disabled tests as required.
Out of Scope Changes check	✅ Passed	All changes are directly related to the stated objective of enforcing base resource alignment limits and re-enabling associated tests, with no extraneous modifications.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[bdice]

/merge