Change wrapping of FLINT Z/nZ polynomial gcd failure #38719
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Two very minor things. Otherwise LGTM.
Co-authored-by: Travis Scrimshaw <[email protected]>
Co-authored-by: Travis Scrimshaw <[email protected]>
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Thank you. Positive review.
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sagemathgh-38719: Change wrapping of FLINT Z/nZ polynomial gcd failure <!-- ^ Please provide a concise and informative title. --> <!-- ^ Don't put issue numbers in the title, do this in the PR description below. --> <!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method to calculate 1 + 2". --> <!-- v Describe your changes below in detail. --> <!-- v Why is this change required? What problem does it solve? --> <!-- v If this PR resolves an open issue, please link to it here. For example, "Fixes sagemath#12345". --> Sometimes FLINT fails to calculate GCDs in polynomial rings over Z/nZ. Since FLINT has no interface to report the failure, the GCD calculation needs to be wrapped and an error thrown. The present method of wrapping does not properly reactivate signals if an error happens, because the exception causes `sig_off()` to never be reached. This patch rectifies that. It also adds a doctest which triggers this code path; the example is designed so that the GCD exists but FLINT fails. The error message is also adjusted, since the failure condition is more complicated than just encountering non-invertible elements (e.g., in Z/6, `gcd(2*x, x)` will work). URL: sagemath#38719 Reported by: Kyle Hofmann Reviewer(s): Kyle Hofmann, Travis Scrimshaw
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Sometimes FLINT fails to calculate GCDs in polynomial rings over Z/nZ. Since FLINT has no interface to report the failure, the GCD calculation needs to be wrapped and an error thrown. The present method of wrapping does not properly reactivate signals if an error happens, because the exception causes
sig_off()to never be reached. This patch rectifies that. It also adds a doctest which triggers this code path; the example is designed so that the GCD exists but FLINT fails.The error message is also adjusted, since the failure condition is more complicated than just encountering non-invertible elements (e.g., in Z/6,
gcd(2*x, x)will work).