[PATCH] D137213: [clang][modules] NFCI: Pragma diagnostic mappings: write/read FileID instead of SourceLocation

[Jan Svoboda via Phabricator via cfe-commits]

jansvoboda11 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");
----------------
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.


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  https://reviews.llvm.org/D137213/new/

https://reviews.llvm.org/D137213