erichkeane added a comment. In D121063#3364833 <https://reviews.llvm.org/D121063#3364833>, @void wrote:
> In D121063#3364815 <https://reviews.llvm.org/D121063#3364815>, @erichkeane > wrote: > >> In D121063#3364810 <https://reviews.llvm.org/D121063#3364810>, @void wrote: >> >>> In D121063#3364780 <https://reviews.llvm.org/D121063#3364780>, @void wrote: >>> >>>> In D121063#3363852 <https://reviews.llvm.org/D121063#3363852>, @erichkeane >>>> wrote: >>>> >>>>> I suspect this works because we never really treated this as a LL, just >>>>> as a pair of iterators. Two things: >>>>> >>>>> 1- Can you produce some situation where this is valuable to do? >>>> >>>> Yes. In the randstruct feature I'm working on, if this code isn't there it >>>> goes into an infinite loop: https://reviews.llvm.org/D120857. It's >>>> possible that the way it's constructing and using the list of Decls is >>>> somehow wrong, but I wasn't able to identify how. >>>> >>>>> 2- Can you switch this over so that the NextInContextAndBits initializes >>>>> to nullptr/0 so that this line isn't necessary? I can't imagine we ever >>>>> re-call this on a decl and have the answer be different. >>>> >>>> I'll give it a shot. I'm with @urnathan though that it should have already >>>> been like that. :-) Probably just an oversight. >>> >>> After looking at the randstruct code again, it's possible that it's not >>> doing the correct thing. (#include "MildShockMeme.h"!) The Decls already >>> have a their pointers set, but then we shuffle them and all Hell breaks >>> loose when we call that function because the end is pointing back to >>> somewhere within the structure beginning. This patch is probably not a bad >>> idea in general, but if you want me to I can fix it on my end. >> >> Ah! Shuffling declarations in a chain is not likely to do 'good things', >> I'm surprised that this is the first issue we've seen!. > > Same :-) > >> I presume that there needs to be a 'RebuildDeclChain' for the purposes of >> 'RandStruct' that first nulls-out the next-in-context-and-bits. > > Without this patch, then yes. It might actually be a better idea to have it > in the DeclContext anyway just in case someone else wants to use it. > >> Alternatively, perhaps "RandStruct" should be 'randomizing' on the first >> call to this BuildDeclChain function. > > I assume that `BuildDeclChain` is called once (and only once) per Record? > Will randomizing when calling `BuildDeclChain` mess up the ABI somehow? Or is > it safer to do it here because the ABI is decided afterwards? Interestingly, the ONLY call I see to this is via calls of `LoadLexicalDeclsFromExternalStorage` and `RecordDecl::LoadFieldsFromexternalStorage`. I suspect that the purpose of this is only for restoring the declaration list after loading a module of some sort. I see this is the origin of the record-fields one: https://github.com/llvm/llvm-project/commit/0e88a565c0978bb6fd835a33e8069135661a1400 which seems to be most of this function as well. So I don't have a good idea actually of when this would happen. It does NOT seem like something that happens during normal compilation I would expect though. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D121063/new/ https://reviews.llvm.org/D121063 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
