[Modules] Add 'no_undeclared_includes' module map attribute

The 'no_undeclared_includes' attribute should be used in a module to
tell that only non-modular headers and headers from used modules are
accepted.

The main motivation behind this is to prevent dep cycles between system
libraries (such as darwin) and libc++.

Patch by Richard Smith!

llvm-svn: 284797

3 files changed, 20 insertions, 4 deletions

diff --git a/clang/include/clang/Basic/Module.h b/clang/include/clang/Basic/Module.h
index 1702fb1114d..31c5c7ec9ca 100644
--- a/clang/include/clang/Basic/Module.h
+++ b/clang/include/clang/Basic/Module.h
@@ -201,6 +201,10 @@ public:
   /// built.
   unsigned ConfigMacrosExhaustive : 1;
 
+  /// \brief Whether files in this module can only include non-modular headers
+  /// and headers from used modules.
+  unsigned NoUndeclaredIncludes : 1;
+
   /// \brief Describes the visibility of the various names within a
   /// particular module.
   enum NameVisibilityKind {
diff --git a/clang/include/clang/Lex/HeaderSearch.h b/clang/include/clang/Lex/HeaderSearch.h
index 800facbcebf..faba6619511 100644
--- a/clang/include/clang/Lex/HeaderSearch.h
+++ b/clang/include/clang/Lex/HeaderSearch.h
@@ -523,8 +523,10 @@ public:
   /// \brief Retrieve the module that corresponds to the given file, if any.
   ///
   /// \param File The header that we wish to map to a module.
-  ModuleMap::KnownHeader findModuleForHeader(const FileEntry *File) const;
-  
+  /// \param AllowTextual Whether we want to find textual headers too.
+  ModuleMap::KnownHeader findModuleForHeader(const FileEntry *File,
+                                             bool AllowTextual = false) const;
+
   /// \brief Read the contents of the given module map file.
   ///
   /// \param File The module map file.
diff --git a/clang/include/clang/Lex/ModuleMap.h b/clang/include/clang/Lex/ModuleMap.h
index 8a704db2cda..4288a4f506c 100644
--- a/clang/include/clang/Lex/ModuleMap.h
+++ b/clang/include/clang/Lex/ModuleMap.h
@@ -171,7 +171,8 @@ private:
 
   /// \brief The set of attributes that can be attached to a module.
   struct Attributes {
-    Attributes() : IsSystem(), IsExternC(), IsExhaustive() {}
+    Attributes()
+        : IsSystem(), IsExternC(), IsExhaustive(), NoUndeclaredIncludes() {}
 
     /// \brief Whether this is a system module.
     unsigned IsSystem : 1;
@@ -181,6 +182,10 @@ private:
 
     /// \brief Whether this is an exhaustive set of configuration macros.
     unsigned IsExhaustive : 1;
+
+    /// \brief Whether files in this module can only include non-modular headers
+    /// and headers from used modules.
+    unsigned NoUndeclaredIncludes : 1;
   };
 
   /// \brief A directory for which framework modules can be inferred.
@@ -315,10 +320,15 @@ public:
   ///
   /// \param File The header file that is likely to be included.
   ///
+  /// \param AllowTextual If \c true and \p File is a textual header, return
+  /// its owning module. Otherwise, no KnownHeader will be returned if the
+  /// file is only known as a textual header.
+  ///
   /// \returns The module KnownHeader, which provides the module that owns the
   /// given header file.  The KnownHeader is default constructed to indicate
   /// that no module owns this header file.
-  KnownHeader findModuleForHeader(const FileEntry *File);
+  KnownHeader findModuleForHeader(const FileEntry *File,
+                                  bool AllowTextual = false);
 
   /// \brief Retrieve all the modules that contain the given header file. This
   /// may not include umbrella modules, nor information from external sources,