chore(native): declare PyContextVar_* locally for limited-API builds (PROF-15850)

[vlad-scherbich]

Description

pyo3-ffi hides PyContextVar_New / _Get / _Set under not(Py_LIMITED_API). CPython
3.15 builds take PYO3_USE_ABI3_FORWARD_COMPATIBILITY=1 (pyo3-build-config 0.28.3 caps
ABI3_MAX_MINOR at 14), so those symbols vanish and the native module fails with E0425.

This PR declares the three stable C API entry points locally in src/native/contextvar.rs.
Context variables exist since 3.7, so the symbols are on every interpreter we support.

If this merges and nothing else new lands: limited-API contextvar builds compile. No publish,
testrunner, riot, or requires-python change.

Testing

Compiled clean on 3.9, 3.13, and 3.15, with and without the stable-ABI path.

Risks

None. Declarations match the stable C API; they do not change runtime behavior on 3.9–3.14.

Additional Notes

Extracted from #19833 (cc @wconti27). Closes #19908. Same class of fix as #18429.

No release note: internal compile fix, changelog/no-changelog.

Base: #19861. Next: #19905 (testrunner pyenv bump).

[datadog-prod-us1-4]

 

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⚠️ Warnings

❌ Your PR has failed checks. Please review the issues below and take necessary action before merging.

🚦 5 Pipeline jobs failed

DataDog/apm-reliability/dd-trace-py | rust ci — 🔧 Needs a code fix, caused by this PR

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DataDog/apm-reliability/dd-trace-py | debugging/exploration/botocore: [3.12] — 🔄 Retry may pass, looks flaky

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DataDog/apm-reliability/dd-trace-py | profiling_native: [3.13, thread] — 🔄 Retry may pass, looks flaky

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ℹ️ Info

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🧪 All tests passed
❄️ No new flaky tests detected

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[pr-commenter]

Benchmarks

Benchmark execution time: 2026-08-28 16:32:50

Comparing candidate commit bb9aaf9 in PR branch vlad/py315-pyo3-contextvar with baseline commit 5bd6b96 in branch main.

📊 Benchmarking dashboard

Found 0 performance improvements and 7 performance regressions! Performance is the same for 575 metrics, 10 unstable metrics, 2 known flaky benchmarks, 16 flaky benchmarks without significant changes.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

• 🟩 = significantly better candidate vs. baseline
• 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

scenario:httppropagationextract-tracecontext_headers

• 🟥 execution_time [+2.330µs; +2.578µs] or [+7.308%; +8.086%]

scenario:httppropagationinject-ids_only

• 🟥 execution_time [+2.570µs; +2.709µs] or [+15.545%; +16.384%]

scenario:iastaspects-add_aspect

• 🟥 execution_time [+10.303µs; +13.386µs] or [+10.372%; +13.477%]

scenario:iastaspectsospath-ospathbasename_aspect

• 🟥 execution_time [+134.485µs; +142.396µs] or [+32.471%; +34.381%]

scenario:iastaspectssplit-rsplit_aspect

• 🟥 execution_time [+36.684µs; +41.600µs] or [+25.768%; +29.221%]

scenario:telemetryaddmetric-1-count-metric-1-times

• 🟥 execution_time [+637.013ns; +682.242ns] or [+23.846%; +25.539%]

scenario:tracer-small

• 🟥 execution_time [+29.083µs; +31.390µs] or [+8.952%; +9.661%]

Unstable benchmarks

These benchmarks have a confidence interval too wide to call a change; treat them as noise rather than signal.

scenario:coreapiscenario-context_with_data_listeners

• unstable execution_time [-656.499ns; +801.534ns] or [-6.008%; +7.335%]

scenario:coreapiscenario-core_dispatch_1_listener

• unstable execution_time [-33.958ns; +31.883ns] or [-5.553%; +5.213%]

scenario:coreapiscenario-core_dispatch_50_listeners

• unstable execution_time [-1358.135ns; +1911.008ns] or [-8.104%; +11.402%]

scenario:coreapiscenario-core_dispatch_exception_listeners

• unstable execution_time [-895.828ns; +1596.063ns] or [-6.976%; +12.429%]

scenario:coreapiscenario-core_dispatch_listeners

• unstable execution_time [-251.536ns; +395.318ns] or [-6.949%; +10.921%]

scenario:coreapiscenario-core_dispatch_no_args_listeners

• unstable execution_time [-190.197ns; +315.854ns] or [-6.620%; +10.993%]

scenario:coreapiscenario-core_dispatch_with_results_1_listener

• unstable execution_time [-80.205ns; +70.281ns] or [-6.809%; +5.967%]

scenario:coreapiscenario-core_dispatch_with_results_50_listeners

• unstable execution_time [-3963.518ns; +3991.105ns] or [-9.730%; +9.798%]

scenario:coreapiscenario-core_dispatch_with_results_listeners

• unstable execution_time [-846.194ns; +694.760ns] or [-10.453%; +8.583%]

scenario:packagesupdateimporteddependencies-import_many_stdlib_cached

• unstable execution_time [-54.216µs; +63.749µs] or [-8.701%; +10.230%]

Known flaky benchmarks

These benchmarks are marked as flaky and will not trigger a failure. Modify FLAKY_BENCHMARKS_REGEX to control which benchmarks are marked as flaky.

scenario:iastaspects-casefold_noaspect

• 🟥 execution_time [+62.972µs; +69.109µs] or [+25.204%; +27.661%]

scenario:iastaspects-translate_aspect

• 🟥 execution_time [+90.008µs; +97.550µs] or [+20.582%; +22.306%]

Known flaky benchmarks without significant changes:

• scenario:errortrackingflasksqli-baseline
• scenario:flasksimple-iast-get
• scenario:iastaspects-casefold_aspect
• scenario:iastaspects-index_aspect
• scenario:iastaspects-ljust_noaspect
• scenario:iastaspects-lower_aspect
• scenario:iastaspects-replace_aspect
• scenario:iastaspects-swapcase_aspect
• scenario:iastaspects-title_noaspect
• scenario:iastaspects-translate_noaspect
• scenario:iastaspects-upper_noaspect
• scenario:packagespackageforrootmodulemapping-cache_off
• scenario:packagespackageforrootmodulemapping-cache_on
• scenario:sethttpmeta-all-enabled
• scenario:span-start
• scenario:telemetryaddmetric-record-100-metrics

[vlad-scherbich]

Part of #19908

[Copilot]

Pull request overview

This PR fixes Rust native extension builds under Py_LIMITED_API (e.g., CPython 3.15 builds using PYO3_USE_ABI3_FORWARD_COMPATIBILITY) by locally declaring the PyContextVar_New, PyContextVar_Get, and PyContextVar_Set C-API entry points that are not exposed by pyo3-ffi in that configuration.

Changes:

• Add local extern "C" declarations for PyContextVar_* functions in src/native/contextvar.rs.
• Switch call sites from ffi::PyContextVar_* to the locally declared symbols so the module compiles with and without Py_LIMITED_API.

---

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[cit-pr-commenter-54b7da]

Codeowners resolved as

Resolved from the full PR diff against vlad/py315-manylinux-wheels using the target branch CODEOWNERS file.
CODEOWNERS team requests not listed below are not required by the current file set.

src/native/contextvar.rs                                                @DataDog/apm-core-python

[cit-pr-commenter-54b7da]

Circular import analysis

⚠️ Existing circular imports

There are 3 circular imports that already exist on the base branch and have not been changed by this PR.

ddtrace.errortracking._handled_exceptions.bytecode_injector -> ddtrace.errortracking._handled_exceptions.callbacks -> ddtrace.errortracking._handled_exceptions.collector -> ddtrace.errortracking._handled_exceptions.bytecode_reporting -> ddtrace.errortracking._handled_exceptions.bytecode_injector
ddtrace.llmobs -> ddtrace.llmobs._evaluators -> ddtrace.llmobs._evaluators.format -> ddtrace.llmobs._experiment -> ddtrace.llmobs
ddtrace.appsec._asm_request_context -> ddtrace.appsec._iast._iast_request_context_base -> ddtrace.appsec._iast._iast_env -> ddtrace.appsec._iast.reporter -> ddtrace.appsec._exploit_prevention.stack_traces -> ddtrace.appsec._asm_request_context

[cit-pr-commenter-54b7da]

Dependency direction analysis

⚠️ Existing dependency direction violations

There are 240 dependency direction violations that already exist on the base branch and have not been changed by this PR.

Show existing violations (showing 5 of 240 highest severity)

ddtrace.internal.tracemethods -×-> ddtrace.trace  (internal-core -> product:tracing, score=135)
ddtrace.llmobs._integrations.crewai -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=133)
ddtrace.llmobs._integrations.openai_agents -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=133)
ddtrace.profiling.scheduler -×-> ddtrace.trace  (product:profiling -> product:tracing, score=133)
ddtrace.llmobs._integrations.pydantic_ai -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=133)

To see all violations, download the layers-base.json and layers-pr.json artifacts from this CI job and run:

uv run --script scripts/import-analysis/layers.py compare layers-base.json layers-pr.json

[chatgpt-codex-connector]

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.