ARROW-16013: [C++][Python] Signed overflow when using negative stride in NumPyStridedConverter

[zagto]

No description provided.

[github-actions]

https://issues.apache.org/jira/browse/ARROW-16013

[pitrou]

Is it possible to add a test that would fail without this fix?

[zagto]

Not in a way I know of.

• To reliably break it, we could use it on a numpy type, that is not a power of 2 in sizeof(). But that does not seem to exist x86_64. But for example long double on 32-bit x86 is 96-bit sizeof() (?)
• As long is the size is a power of two it depends on the behavior of signed overflow and the binary representation of negative numbers to work/break, which happens to make it work on common platforms.
• It could still break because of compiler optimizations, but then again that is something we can't really control in a test

[pitrou]

Ok, thanks. Can you then add a comment near your change pointing to the issue?

[zagto]

yes, added a comment

[pitrou]

Thank for the update @zagto, will merge.

[ursabot]

Benchmark runs are scheduled for baseline = 5cedd25 and contender = 6773da1. 6773da1 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Finished ⬇️0.0% ⬆️0.0%] ec2-t3-xlarge-us-east-2
[Finished ⬇️1.01% ⬆️0.04%] test-mac-arm
[Finished ⬇️5.71% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.26% ⬆️0.0%] ursa-thinkcentre-m75q
Buildkite builds:
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ec2-t3-xlarge-us-east-2/builds/402| 6773da12 ec2-t3-xlarge-us-east-2>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-test-mac-arm/builds/388| 6773da12 test-mac-arm>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ursa-i9-9960x/builds/388| 6773da12 ursa-i9-9960x>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ursa-thinkcentre-m75q/builds/398| 6773da12 ursa-thinkcentre-m75q>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ec2-t3-xlarge-us-east-2/builds/401| 5cedd25e ec2-t3-xlarge-us-east-2>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-test-mac-arm/builds/387| 5cedd25e test-mac-arm>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ursa-i9-9960x/builds/387| 5cedd25e ursa-i9-9960x>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ursa-thinkcentre-m75q/builds/397| 5cedd25e ursa-thinkcentre-m75q>
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java