[PATCH] D113676: WIP: [clang][lex] Fix search path usage remark with modules

[Alex Hoppen via Phabricator via cfe-commits]

ahoppen added inline comments.


================
Comment at: clang/lib/Lex/HeaderSearch.cpp:95
+      if (HS.CurrentSearchPathIdx != ~0U)
+        HS.ModuleToSearchDirIdx[M] = HS.CurrentSearchPathIdx;
+    }
----------------
These indices will be out of date if the search paths are changed via `HeaderSearch::SetSearchPaths` or `HeaderSearch::AddSearchPath` after the first module map has been loaded. One could probably adjust the indices in `AddSearchPath` but maybe it’s easier to not use the index into `SearchDirs` as the key. An alternative suggestion would be to use `std::shared_ptr<DirectoryLookup>` instead, changing some of the data structures as follows:
```
- std::vector<DirectoryLookup> SearchDirs
+ std::vector<std::shared_ptr<DirectoryLookup>> SearchDirs

- std::vector<bool> SearchDirsUsage;
+ std::map<std::shared_ptr<DirectoryLookup>, bool> SearchDirsUsage; 

- llvm::DenseMap<Module *, unsigned> ModuleToSearchDirIdx;
+ llvm::DenseMap<Module *, std::shared_ptr<DirectoryLookup>> ModuleToSearchDirIdx;

- llvm::DenseMap<unsigned, unsigned> SearchDirToHSEntry;
+ llvm::DenseMap<std::shared_ptr<DirectoryLookup>, unsigned> SearchDirToHSEntry; 
```


Repository:
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https://reviews.llvm.org/D113676