[Modules] When things go horribly wrong when reading a module, point at the module cache.

Sometimes people hack on their system headers. In such cases, they'll
need to delete their module cache, but may not know where it is. Add a
note to show them where it is.

llvm-svn: 181638

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 4a1ad260e32..17f01380ed0 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -759,6 +759,10 @@ bool ASTReader::ReadDeclContextStorage(ModuleFile &M,
 
 void ASTReader::Error(StringRef Msg) {
   Error(diag::err_fe_pch_malformed, Msg);
+  if (Context.getLangOpts().Modules && !Diags.isDiagnosticInFlight()) {
+    Diag(diag::note_module_cache_path)
+      << PP.getHeaderSearchInfo().getModuleCachePath();
+  }
 }
 
 void ASTReader::Error(unsigned DiagID,
@@ -1715,6 +1719,10 @@ InputFile ASTReader::getInputFile(ModuleFile &F, unsigned ID, bool Complain) {
          )) {
       if (Complain) {
         Error(diag::err_fe_pch_file_modified, Filename, F.FileName);
+        if (Context.getLangOpts().Modules && !Diags.isDiagnosticInFlight()) {
+          Diag(diag::note_module_cache_path)
+            << PP.getHeaderSearchInfo().getModuleCachePath();
+        }
       }
 
       IsOutOfDate = true;