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Make Linker.backend a classmethod#1910

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cpcloud wants to merge 3 commits intoNVIDIA:mainfrom
cpcloud:linker-backend-classmethod-714
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Make Linker.backend a classmethod#1910
cpcloud wants to merge 3 commits intoNVIDIA:mainfrom
cpcloud:linker-backend-classmethod-714

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@cpcloud cpcloud commented Apr 14, 2026 •
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Summary

  • Converts Linker.backend from an instance property to a classmethod so callers can query the linking backend without constructing a Linker
  • Classmethod calls _decide_nvjitlink_or_driver() (existing memoised probe) and maps the return value to "nvJitLink" or "driver"
  • Updates the one in-repo call site in _program.pyx and existing test assertion to use parens
  • Adds 6 GPU-free tests via monkeypatch (no Device() / cuInit required)
  • Adds 0.8.0-notes.rst documenting the breaking change

Breaking change: linker.backend (attribute access) now returns a bound method, not a string. All call sites must use Linker.backend(). Only 2 in-repo call sites affected; numba-cuda (the requester) will adopt Linker.backend() from day one.

Test plan

  • 6 GPU-free tests pass locally (monkeypatch on module globals)
  • CI: existing GPU test test_linker_init passes with updated paren call
  • CI: Cython compile succeeds

Closes #714

🤖 Generated with Claude Code

@cpcloud cpcloud added this to the cuda.core v1.0.0 milestone Apr 14, 2026
@cpcloud cpcloud added enhancement Any code-related improvements P0 High priority - Must do! cuda.core Everything related to the cuda.core module breaking Breaking changes are introduced labels Apr 14, 2026
@cpcloud cpcloud self-assigned this Apr 14, 2026
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github-actions Bot commented Apr 14, 2026

Doc Preview CI

🚀 View preview at
https://nvidia.github.io/cuda-python/pr-preview/pr-1910/

https://nvidia.github.io/cuda-python/pr-preview/pr-1910/cuda-core/

https://nvidia.github.io/cuda-python/pr-preview/pr-1910/cuda-bindings/

https://nvidia.github.io/cuda-python/pr-preview/pr-1910/cuda-pathfinder/


Preview will be ready when the GitHub Pages deployment is complete.

@cpcloud cpcloud force-pushed the linker-backend-classmethod-714 branch 2 times, most recently from dbe6176 to 215418a Compare April 16, 2026 21:45
@cpcloud cpcloud requested a review from leofang April 17, 2026 12:58
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leofang requested changes Apr 21, 2026
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Thanks, Phillip! Implementation-wise LGTM. Left a few suggestions.

Comment thread cuda_core/docs/source/release/1.0.0-notes.rst
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@leofang leofang Apr 21, 2026

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I believe we are shooting for 1.0.0, unless @mdboom concludes that a 0.8.0 is a must for RAPIDS adoption.

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@cpcloud cpcloud Apr 21, 2026

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Renamed to 1.0.0-notes.rst.

Comment thread cuda_core/tests/test_linker_backend.py Outdated
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@leofang leofang Apr 21, 2026

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nit: let's move the tests to the existing test_linker.py. There is no need for separate test files.

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@cpcloud cpcloud Apr 21, 2026

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Moved into test_linker.py and deleted test_linker_backend.py.

Comment thread cuda_core/tests/test_linker_backend.py Outdated
Comment on lines +7 to +9
These live in a separate file from test_linker.py because that module calls
Device() at import time, which requires a GPU. These tests use monkeypatch
to set module-level flags and never touch CUDA devices.
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@leofang leofang Apr 21, 2026

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Does this make sense? Would the driver cuLink* APIs be functional when there is no GPU present? I don't think this is ever tested.

NVRTC/nvJitLink work without GPU or CUDA, but it is not something we want to guarantee to users without the compiler team onboarding. This is not documented AFAIK.

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@cpcloud cpcloud Apr 21, 2026

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Good point — test_linker.py already calls Device() at module import (line 11), so the GPU-free framing was moot. Dropped the rationale and merged the tests in; they just sit alongside the existing ones now.

Comment thread cuda_core/docs/source/release/1.0.0-notes.rst
Comment on lines +13 to +17
- :meth:`Linker.backend` is now a classmethod instead of an instance property.
Call sites must use ``Linker.backend()`` (with parentheses) instead of
``linker.backend``. This allows querying the linking backend without
constructing a ``Linker`` instance — for example, to choose between PTX and
LTOIR input before linking.
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@leofang leofang Apr 21, 2026

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👍

cpcloud added 3 commits April 21, 2026 11:14
@cpcloud
feat(core): convert Linker.backend from property to classmethod
432771c 
Allows querying the linking backend without constructing a Linker
instance — useful for dispatching on input format (PTX vs. LTOIR)
before linking.

Updates existing call sites (Program init, test_linker) to use the
new invocation form Linker.backend().
@cpcloud
test(core): add tests for Linker.backend classmethod
6327b22 
Covers classmethod invocation (Linker.backend() without an instance),
memoisation flag handling, probe-on-first-use, and non-property
attribute semantics.
@cpcloud
docs(core): add 1.0.0 release notes for Linker.backend change
12d291b 
Breaking change: Linker.backend is now a classmethod, so call sites
must use parens: Linker.backend().
@cpcloud cpcloud force-pushed the linker-backend-classmethod-714 branch from 215418a to 12d291b Compare April 21, 2026 15:21
@cpcloud cpcloud requested a review from leofang April 21, 2026 19:48
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breaking Breaking changes are introduced cuda.core Everything related to the cuda.core module enhancement Any code-related improvements P0 High priority - Must do!

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[FEA]: Make Linker.backend a classmethod

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