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

[Jan Svoboda via Phabricator via cfe-commits]

jansvoboda11 created this revision.
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When looking for module, `HeaderSearch::lookupModule` iterates through search paths, parses modulemaps, eagerly creates `Module` instances and caches them in `ModuleMap`. When first called, it will correctly note usage of the search path that discovered the returned module. On subsequent calls, however, it can pull previously created `Module` from `ModuleMap` without noting the search path was used.

This patch fixes that. This requires `HeaderSearch` to be able to go from `Module` to the index of corresponding search path. This is achieved by adding a callback to the modulemap parser, intercepting creations of `Module` instances and pairing them with the current search path index.

The outlined solution doesn't handle all corner cases, though. It's possible for clients to use `HeaderSearch` to lookup module `B`, which could deserialize unrelated modulemap and create instance of module `A`. The client can then look up module `A` directly in `ModuleMap`, avoiding the logic in `HeaderSearch` that makes `-Rsearch-path-usage` work.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113676

Files:
  clang/include/clang/Lex/HeaderSearch.h
  clang/include/clang/Lex/ModuleMap.h
  clang/lib/Lex/HeaderSearch.cpp
  clang/lib/Lex/ModuleMap.cpp
  clang/lib/Serialization/ASTReader.cpp
  clang/test/Preprocessor/search-path-usage-modules.m
  clang/test/Preprocessor/search-path-usage.m

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