4 files changed, 27 insertions, 4 deletions
diff --git a/include/clang/Basic/DiagnosticFrontendKinds.td b/include/clang/Basic/DiagnosticFrontendKinds.td
index 230a6d3dcc..111622e0fe 100644
--- a/include/clang/Basic/DiagnosticFrontendKinds.td
+++ b/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -137,5 +137,11 @@ def warn_missing_submodule : Warning<"missing submodule '%0'">,
 def err_module_map_temp_file : Error<
   "unable to write temporary module map file '%0'">, DefaultFatal;
 def err_module_unavailable : Error<"module '%0' requires feature '%1'">;
-
+def warn_module_config_macro_undef : Warning<
+  "%select{definition|#undef}0 of configuration macro '%1' has no effect on "
+  "the import of '%2'; pass '%select{-D%1=...|-U%1}0' on the command line "
+  "to configure the module">,
+  InGroup<ConfigMacros>;
+def note_module_def_undef_here : Note<
+  "macro was %select{defined|#undef'd}0 here">;
 }
diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td
index 0f127bf2e2..9af83b10a7 100644
--- a/include/clang/Basic/DiagnosticGroups.td
+++ b/include/clang/Basic/DiagnosticGroups.td
@@ -47,6 +47,7 @@ def CastAlign : DiagGroup<"cast-align">;
 def : DiagGroup<"cast-qual">;
 def : DiagGroup<"char-align">;
 def Comment : DiagGroup<"comment">;
+def ConfigMacros : DiagGroup<"config-macros">;
 def : DiagGroup<"ctor-dtor-privacy">;
 def GNUDesignator : DiagGroup<"gnu-designator">;
 
diff --git a/include/clang/Basic/DiagnosticLexKinds.td b/include/clang/Basic/DiagnosticLexKinds.td
index 7f66a87d61..80c52492f4 100644
--- a/include/clang/Basic/DiagnosticLexKinds.td
+++ b/include/clang/Basic/DiagnosticLexKinds.td
@@ -532,6 +532,10 @@ def err_mmap_export_module_id : Error<
   "expected an exported module name or '*'">;
 def err_mmap_expected_library_name : Error<
   "expected %select{library|framework}0 name as a string">;
+def err_mmap_config_macro_submodule : Error<
+  "configuration macros are only allowed on top-level modules">;
+def err_mmap_expected_config_macro : Error<
+  "expected configuration macro name after ','">;
 def err_mmap_missing_module_unqualified : Error<
   "no module named '%0' visible from '%1'">;
 def err_mmap_missing_module_qualified : Error<
diff --git a/include/clang/Basic/Module.h b/include/clang/Basic/Module.h
index 5f081e0f56..2add58019f 100644
--- a/include/clang/Basic/Module.h
+++ b/include/clang/Basic/Module.h
@@ -119,7 +119,14 @@ public:
   /// \brief Whether, when inferring submodules, the inferr submodules should
   /// export all modules they import (e.g., the equivalent of "export *").
   unsigned InferExportWildcard : 1;
-  
+
+  /// \brief Whether the set of configuration macros is exhaustive.
+  ///
+  /// When the set of configuration macros is exhaustive, meaning
+  /// that no identifier not in this list should affect how the module is
+  /// built.
+  unsigned ConfigMacrosExhaustive : 1;
+
   /// \brief Describes the visibility of the various names within a
   /// particular module.
   enum NameVisibilityKind {
@@ -190,6 +197,10 @@ public:
   /// an entity from this module is used.
   llvm::SmallVector<LinkLibrary, 2> LinkLibraries;
 
+  /// \brief The set of "configuration macros", which are macros that
+  /// (intentionally) change how this module is built.
+  std::vector<std::string> ConfigMacros;
+
   /// \brief Construct a top-level module.
   explicit Module(StringRef Name, SourceLocation DefinitionLoc,
                   bool IsFramework)
@@ -197,7 +208,8 @@ public:
       IsAvailable(true), IsFromModuleFile(false), IsFramework(IsFramework), 
       IsExplicit(false), IsSystem(false),
       InferSubmodules(false), InferExplicitSubmodules(false),
-      InferExportWildcard(false), NameVisibility(Hidden) { }
+      InferExportWildcard(false), ConfigMacrosExhaustive(false),
+      NameVisibility(Hidden) { }
   
   /// \brief Construct a new module or submodule.
   Module(StringRef Name, SourceLocation DefinitionLoc, Module *Parent, 
@@ -328,7 +340,7 @@ public:
   ///
   /// \returns The submodule if found, or NULL otherwise.
   Module *findSubmodule(StringRef Name) const;
-  
+
   typedef std::vector<Module *>::iterator submodule_iterator;
   typedef std::vector<Module *>::const_iterator submodule_const_iterator;