[Tooling] Add -x flags when inferring compile commands for files with no/invalid extension.

Summary: We treat them as headers, as the motivating case is C++ standard library.

Reviewers: kadircet

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D61633

llvm-svn: 360153

1 files changed, 7 insertions, 4 deletions

diff --git a/clang/lib/Tooling/InterpolatingCompilationDatabase.cpp b/clang/lib/Tooling/InterpolatingCompilationDatabase.cpp
index 5124340892f..8b1030f3607 100644
--- a/clang/lib/Tooling/InterpolatingCompilationDatabase.cpp
+++ b/clang/lib/Tooling/InterpolatingCompilationDatabase.cpp
@@ -205,10 +205,13 @@ struct TransferableCommand {
     bool TypeCertain;
     auto TargetType = guessType(Filename, &TypeCertain);
     // If the filename doesn't determine the language (.h), transfer with -x.
-    if (TargetType != types::TY_INVALID && !TypeCertain && Type) {
-      TargetType = types::onlyPrecompileType(TargetType) // header?
-                       ? types::lookupHeaderTypeForSourceType(*Type)
-                       : *Type;
+    if ((!TargetType || !TypeCertain) && Type) {
+      // Use *Type, or its header variant if the file is a header.
+      // Treat no/invalid extension as header (e.g. C++ standard library).
+      TargetType =
+          (!TargetType || types::onlyPrecompileType(TargetType)) // header?
+              ? types::lookupHeaderTypeForSourceType(*Type)
+              : *Type;
       if (ClangCLMode) {
         const StringRef Flag = toCLFlag(TargetType);
         if (!Flag.empty())