[clang] [analyzer] MallocChecker: Recognize std::atomics in smart pointer suppression. (PR #90918)

[Artem Dergachev via cfe-commits]

haoNoQ wrote:

@sharkautarch Yeah I think the situation where we observe the allocation site during analysis may be significantly different in presence of smart pointers. It may be a good idea to include such check in the heuristic, to reclaim some of the false negatives currently silenced by it. If we've seen the initial reference count and we've modeled it perfectly so far, these false positives can't happen. But this implies that we model our atomics perfectly. And given that we don't even know what a "reference count" is (maybe it's just some unrelated integer?), it's quite hard to get that right.

Also we don't really do "whole program analysis" and we probably can't do that without major changes to our technique; it simply doesn't scale to that scale. Our existing cross-TU mode is more about _occasionally_ breaking translation unit boundaries when we really want something specific from another TU (like the effects of a function call we just encountered), but we still focus on small portions of the program at a time. We never really derive whole-program conclusions from these small independent invocations of our analysis. That'd require very different technology. It's not necessarily difficult per se – we could develop such technology and occasionally make our main analysis interoperate with it. But we haven't done any of that yet and our cross-TU mode isn't that kind of cross-TU mode.

https://github.com/llvm/llvm-project/pull/90918