1 files changed, 31 insertions, 0 deletions
diff --git a/include/clang/Basic/SourceManager.h b/include/clang/Basic/SourceManager.h
index 5717816ff9..bd31c79ba2 100644
--- a/include/clang/Basic/SourceManager.h
+++ b/include/clang/Basic/SourceManager.h
@@ -40,6 +40,7 @@
 #include "clang/Basic/SourceLocation.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/DataTypes.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
@@ -508,6 +509,11 @@ public:
 
 };
 
+/// \brief The path used when building modules on demand, which is used
+/// to provide a link between the source managers of the different compiler
+/// instances.
+typedef llvm::ArrayRef<std::pair<std::string, FullSourceLoc> > ModuleBuildPath;
+
 /// \brief This class handles loading and caching of source files into memory.
 ///
 /// This object owns the MemoryBuffer objects for all of the loaded
@@ -645,6 +651,15 @@ class SourceManager : public RefCountedBase<SourceManager> {
 
   mutable llvm::DenseMap<FileID, MacroArgsMap *> MacroArgsCacheMap;
 
+  /// \brief The path of modules being built, which is used to detect
+  /// cycles in the module dependency graph as modules are being built, as
+  /// well as to describe 
+  ///
+  /// There is no way to set this value from the command line. If we ever need
+  /// to do so (e.g., if on-demand module construction moves out-of-process),
+  /// we can add a cc1-level option to do so.
+  SmallVector<std::pair<std::string, FullSourceLoc>, 2> StoredModuleBuildPath;
+
   // SourceManager doesn't support copy construction.
   explicit SourceManager(const SourceManager&) LLVM_DELETED_FUNCTION;
   void operator=(const SourceManager&) LLVM_DELETED_FUNCTION;
@@ -669,6 +684,22 @@ public:
   /// (likely to change while trying to use them).
   bool userFilesAreVolatile() const { return UserFilesAreVolatile; }
 
+  /// \brief Retrieve the module build path.
+  ModuleBuildPath getModuleBuildPath() const {
+    return StoredModuleBuildPath;
+  }
+
+  /// \brief Set the module build path.
+  void setModuleBuildPath(ModuleBuildPath path) {
+    StoredModuleBuildPath.clear();
+    StoredModuleBuildPath.append(path.begin(), path.end());
+  }
+
+  /// \brief Append an entry to the module build path.
+  void appendModuleBuildPath(StringRef moduleName, FullSourceLoc importLoc) {
+    StoredModuleBuildPath.push_back(std::make_pair(moduleName.str(),importLoc));
+  }
+
   /// \brief Create the FileID for a memory buffer that will represent the
   /// FileID for the main source.
   ///