fix: silence Coverity UNUSED_VALUE in __create_descriptor_1d - #365
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The value returned by DftiFreeDescriptor on the reallocate path is consumed only by a debug-only assert(status == 0). Under NDEBUG the assert is stripped, so the store is dead before the unconditional status = 0 reset, which Coverity flags as UNUSED_VALUE (one CID per .c.src template instantiation). Mark the value as intentionally unused with (void)status to make the intent explicit and clear the finding.
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Backport of IntelPython/mkl_umath#266, adapted to mkl_fft. - Pin cython==3.3.0 in the Coverity workflow (only there, not in pyproject.toml) so the generated _pydfti.c stays byte-stable between scans and Coverity CIDs plus their triage survive. Works because the scan build uses --no-build-isolation. - Add coverity/README.md: where findings come from across mkl_fft's two translation units (template-generated mklfft.c, which is our DFTI logic and stays in scope, and Cython-generated _pydfti.c), the Cython-pin rationale, an opt-in Project Component, a review checklist, and the verified false-positive families for the mkl_fft project. The known false positives are grouped by checker + mechanism from the current scan: Cython-generated boilerplate (tp_traverse DEADCODE, version/ABI-guarded helper DEADCODE, a reference-cleanup UNUSED_VALUE, a CHECKED_RETURN) and two dead-by-construction families in our own .pyx (redundant is-NULL guards Cython already proves, and an intentional in-place placeholder stub) - all triaged Intentional / Ignore. The genuine __create_descriptor_1d UNUSED_VALUE defects were fixed in #365, not suppressed, so mklfft.c stays in scope. mkl_umath's own documented false positives were not ported blind; the table was rebuilt from mkl_fft's own scan and generated code.
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The PR resolves the Coverity UNUSED_VALUE (CWE-563) findings in
__create_descriptor_1d_*.On the
reallocate:path in mkl_fft/src/mklfft.c.src, the value returned byDftiFreeDescriptoris stored intostatusbut consumed only by the debug-onlyassert(status == 0). UnderNDEBUGthe assert is compiled out, so the store is dead before the unconditionalstatus = 0;reset — which Coverity flags.The behavior is correct as written (the old handle's free status is irrelevant since a fresh descriptor is built next). This marks the value as intentionally unused with
(void)status;to make the intent explicit and clear the finding.