[PATCH] D71406: [clangd] Add xref for macros to FileIndex.

[Haojian Wu via Phabricator via cfe-commits]

hokein added a comment.

@ilya-biryukov thanks for taking it during my OOO, just a drive-by comment :)



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Comment at: clang-tools-extra/clangd/index/FileIndex.cpp:86
+    // Add macro references.
+    for (const auto &IDToRefs : MacroRefsToIndex->MacroRefs) {
+      for (const auto &Range : IDToRefs.second) {
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ilya-biryukov wrote:
> This is trying to emulate existing logic in `SymbolCollector::finish`. Is there a way we could share this?
> Would avoid creating extra copies of reference slabs and allow to keep the code in one place, rather than scattering it between `FileIndex.cpp` and `SymbolCollector.cpp`. Would also allow to keep `toURI` private, meaning we don't have to worry about naming it and the fact it's exposed in the public interface.
> 
> One potential way to do this is to have an alternative version of `handleMacroOccurence`, which would fill `SymbolCollector::MacroRefs` directly and call this right after `indexTopLevelDecls`.
> Would that work?
+1 on the concern about performance (this is a hot function, we are paying an extra cost of copying all refs, which should be avoided), and the layering of `toURI`.

> One potential way to do this is to have an alternative version of handleMacroOccurence, which would fill SymbolCollector::MacroRefs directly and call this right after indexTopLevelDecls.
> Would that work?

the main problem is that at this point (parsing is finished), preprocessor callback is not available, so we won't see macro references (`SymbolCollector::handleMacroOccurence` will only receive macro definitions).

I think two options:
- as mentioned above, add alternative version of `handleMacroOccurence` in SymbolCollector, calling it **before** `indexTopLevelDecls` (because `finish` is called in `indexTopLevelDecls` which we have no way to customize);
- or we could add a finish callback to the `SymbolCollector` which is called in `SymbolCollector::finish`, and put this logic to the callback.



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  https://reviews.llvm.org/D71406/new/

https://reviews.llvm.org/D71406