3 files changed, 17 insertions, 7 deletions
diff --git a/clang-tools-extra/clangd/index/CanonicalIncludes.cpp b/clang-tools-extra/clangd/index/CanonicalIncludes.cpp
index 017547ce057..55df267c4fa 100644
--- a/clang-tools-extra/clangd/index/CanonicalIncludes.cpp
+++ b/clang-tools-extra/clangd/index/CanonicalIncludes.cpp
@@ -86,16 +86,25 @@ collectIWYUHeaderMaps(CanonicalIncludes *Includes) {
   return llvm::make_unique<PragmaCommentHandler>(Includes);
 }
 
-void addSystemHeadersMapping(CanonicalIncludes *Includes) {
+void addSystemHeadersMapping(CanonicalIncludes *Includes,
+                             const LangOptions &Language) {
   static const std::vector<std::pair<const char *, const char *>> SymbolMap = {
 #define SYMBOL(Name, NameSpace, Header) { #NameSpace#Name, #Header },
       #include "StdSymbolMap.inc"
 #undef SYMBOL
   };
-
-  for (const auto &Pair : SymbolMap)
-    Includes->addSymbolMapping(Pair.first, Pair.second);
-
+  static const std::vector<std::pair<const char *, const char *>> CSymbolMap = {
+#define SYMBOL(Name, NameSpace, Header) { #Name, #Header },
+      #include "CSymbolMap.inc"
+#undef SYMBOL
+  };
+  if (Language.CPlusPlus) {
+    for (const auto &Pair : SymbolMap)
+      Includes->addSymbolMapping(Pair.first, Pair.second);
+  } else if (Language.C11) {
+    for (const auto &Pair : CSymbolMap)
+      Includes->addSymbolMapping(Pair.first, Pair.second);
+  }
   // FIXME: remove the std header mapping once we support ambiguous symbols, now
   // it serves as a fallback to disambiguate:
   //   - symbols with mulitiple headers (e.g. std::move)
diff --git a/clang-tools-extra/clangd/index/CanonicalIncludes.h b/clang-tools-extra/clangd/index/CanonicalIncludes.h
index f85b76bf2a1..4d1b8517e9a 100644
--- a/clang-tools-extra/clangd/index/CanonicalIncludes.h
+++ b/clang-tools-extra/clangd/index/CanonicalIncludes.h
@@ -84,7 +84,8 @@ collectIWYUHeaderMaps(CanonicalIncludes *Includes);
 ///   - Compiler extensions, e.g. include/avx512bwintrin.h$ -> <immintrin.h>
 /// The mapping is hardcoded and hand-maintained, so it might not cover all
 /// headers.
-void addSystemHeadersMapping(CanonicalIncludes *Includes);
+void addSystemHeadersMapping(CanonicalIncludes *Includes,
+                             const LangOptions &Language);
 
 } // namespace clangd
 } // namespace clang
diff --git a/clang-tools-extra/clangd/index/IndexAction.cpp b/clang-tools-extra/clangd/index/IndexAction.cpp
index d3bb8ef818a..8de0e75ab29 100644
--- a/clang-tools-extra/clangd/index/IndexAction.cpp
+++ b/clang-tools-extra/clangd/index/IndexAction.cpp
@@ -128,6 +128,7 @@ public:
   std::unique_ptr<ASTConsumer>
   CreateASTConsumer(CompilerInstance &CI, llvm::StringRef InFile) override {
     CI.getPreprocessor().addCommentHandler(PragmaHandler.get());
+    addSystemHeadersMapping(Includes.get(), CI.getLangOpts());
     if (IncludeGraphCallback != nullptr)
       CI.getPreprocessor().addPPCallbacks(
           llvm::make_unique<IncludeGraphCollector>(CI.getSourceManager(), IG));
@@ -200,7 +201,6 @@ std::unique_ptr<FrontendAction> createStaticIndexingAction(
     Opts.RefsInHeaders = true;
   }
   auto Includes = llvm::make_unique<CanonicalIncludes>();
-  addSystemHeadersMapping(Includes.get());
   Opts.Includes = Includes.get();
   return llvm::make_unique<IndexAction>(
       std::make_shared<SymbolCollector>(std::move(Opts)), std::move(Includes),