steven_wu added a comment. In D141625#4052869 <https://reviews.llvm.org/D141625#4052869>, @rsmith wrote:
> In D141625#4052820 <https://reviews.llvm.org/D141625#4052820>, @dblaikie > wrote: > >> Yeah, might be nice to document where the instability comes from - if it >> comes from a DenseMap or similar, then a test that fails either in forward >> or reverse iteration mode would be nice to have. > > `Scope::decls` is iterating over a `SmallPtrSet`. This might be a little > annoying to create a test for, because it'll only be unstable if we have two > decls in the same prototype scope that get allocated into different slabs by > the bump ptr allocator, but maybe something like: > > void f(struct A *p, int arr[1 + 0 + 0 + 0 + ... + 0], struct B *q); > > ... would be enough (with sufficient subexpressions to fill a whole slab). > Then we can build a .pch for that twice and check that it comes out identical. Yeah, it is really hard to trigger a failure. Even the second decl gets onto a different slab, the second slab will most likely come after the previous one when there isn't much memory pressure. I can write a test like that but it is really hard to trigger without an enormous module (building Darwin module from macOS SDK can reproduce very reliable). Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D141625/new/ https://reviews.llvm.org/D141625 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
