[clang] [clang-tools-extra] [clang-tidy][dataflow] Add `bugprone-null-check-after-dereference` check (PR #84166)

[Yitzhak Mandelbaum via cfe-commits]

ymand wrote:

> My main problem is that dataflow framework is slow and unstable, there are 20 issues open for an bugprone-unchecked-optional-access check that uses this framework and 19 issues for a framework alone. It crashes, it hangs and only cause problems.

I think those issues are stale. We've done a huge amount of stability engineering in the past 6 months and are running multiple checks based on this framework ~daily over our entire (> 500 MLoc) codebase with no known crashes.

The same goes for speed - it's definitely more expensive than typical, local, clang tidies, but we've made significant improvements in this area as well, and track performance of our nullability check with benchmark tests.

More generally, I think that if we push folks away from experimental clang tidy checks because of stability, we'll shut down experimentation for clang tidy. Is there no way to mark new/experimental checks so that they are off by default?


https://github.com/llvm/llvm-project/pull/84166