alexfh added a subscriber: jgorbe.
alexfh added inline comments.
================
Comment at: clang/lib/Serialization/ASTReader.cpp:6343
"Invalid data, missing pragma diagnostic states");
- SourceLocation Loc = ReadSourceLocation(F, Record[Idx++]);
- auto IDAndOffset = SourceMgr.getDecomposedLoc(Loc);
- assert(IDAndOffset.first.isValid() && "invalid FileID for transition");
- assert(IDAndOffset.second == 0 && "not a start location for a FileID");
+ FileID FID = ReadFileID(F, Record, Idx);
+ assert(FID.isValid() && "invalid FileID for transition");
----------------
jansvoboda11 wrote:
> alexfh wrote:
> > dexonsmith wrote:
> > > eaeltsin wrote:
> > > > This doesn't work as before, likely because ReadFileID doesn't do
> > > > TranslateSourceLocation.
> > > >
> > > > Our tests fail.
> > > >
> > > > I tried calling TranslateSourceLocation here and the tests passed:
> > > > ```
> > > > SourceLocation Loc = Diag.SourceMgr->getComposedLoc(FID, 0);
> > > > SourceLocation Loc2 = TranslateSourceLocation(F, Loc);
> > > > auto IDAndOffset = SourceMgr.getDecomposedLoc(Loc2);
> > > >
> > > > // Note that we don't need to set up Parent/ParentOffset here,
> > > > because
> > > > // we won't be changing the diagnostic state within imported
> > > > FileIDs
> > > > // (other than perhaps appending to the main source file, which
> > > > has no
> > > > // parent).
> > > > auto &F = Diag.DiagStatesByLoc.Files[IDAndOffset.first];
> > > > ```
> > > >
> > > > Sorry I don't know the codebase, so this fix is definitely ugly :) But
> > > > it shows the problem.
> > > >
> > > I don't think that's the issue, since `ReadFileID()` calls
> > > `TranslateFileID`, which should seems like it should be equivalent.
> > >
> > > However, I notice that the post-increment for `Idx` got dropped! Can you
> > > try replacing the line of code with the following and see if that fixes
> > > your tests (without any extra TranslateSourceLocation logic)?
> > > ```
> > > lang=c++
> > > FileID FID = ReadFileID(F, Record, Idx++);
> > > ```
> > >
> > > If so, maybe you can contribute that fix with a reduced testcase? I
> > > suggest adding me, @vsapsai, @Bigcheese, and @jansvoboda11 as reviewers.
> > >
> > > @alexfh, maybe you can check if this fixes your tests as well?
> > >
> > > (If this is the issue, it's a bit surprising we don't have existing tests
> > > covering this case... and embarrassing I missed it when reviewing
> > > initially!)
> > I've noticed the dropped `Idx` post-increment as well, but I went a step
> > further and looked at the `ReadFileID` implementation, which is actually
> > doing a post-increment itself, and accepts `Idx` by reference:
> > ```
> > FileID ReadFileID(ModuleFile &F, const RecordDataImpl &Record,
> > unsigned &Idx) const {
> > return TranslateFileID(F, FileID::get(Record[Idx++]));
> > }
> > ```
> >
> > Thus, it seems to be correct. But what @eaeltsin has found is actually a
> > problem for us. I'm currently trying to make an isolated test case, but
> > it's quite tricky (as header modules are =\). It may be the case that our
> > build setup relies on something clang doesn't explicitly promises, but the
> > fact is that the behavior (as observed by our build setup) has changed.
> > I'll try to revert the commit for now to get us unblocked and provide a
> > test case as soon as I can.
> Thanks for helping out @dexonsmith, we did have the week off.
>
> @eaeltsin @alexfhDone, are you able to provide the failing test case? I'm
> happy to look into it and re-land this with a fix.
I've spent multiple hours trying to extract an observable test case. It turned
out to be too hairy of a yaq to shave: for each compilation a separate
sandboxed environment is created with a separate symlink tree with just the
inputs necessary for that action. Some of the inputs are prebuilt module files
(e.g. for libc++) that are version-locked with the compiler. So far @jgorbe and
I could reduce this to four compilation steps with their own symlink trees with
inputs. While I could figure out some of the factors that affect
reproducibility (for example, symlinks are important, since making a deep copy
of the input directories makes the issue disappear), it will take a few more
hours of concentrated yak shaving to bring this to a shareable state. I'm not
sure I have much more time to sink into investigating this.
It seems like examining code based on @eaeltsin's finding may be a more
fruitful path to synthesizing a regression test. Could you try following that
path?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D137213/new/
https://reviews.llvm.org/D137213
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