Index: cfe/trunk/include/clang/Tooling/CompilationDatabase.h
===================================================================
--- cfe/trunk/include/clang/Tooling/CompilationDatabase.h
+++ cfe/trunk/include/clang/Tooling/CompilationDatabase.h
@@ -64,10 +64,12 @@
 
 /// \brief Interface for compilation databases.
 ///
-/// A compilation database allows the user to retrieve all compile command lines
-/// that a specified file is compiled with in a project.
-/// The retrieved compile command lines can be used to run clang tools over
-/// a subset of the files in a project.
+/// A compilation database allows the user to retrieve compile command lines
+/// for the files in a project.
+///
+/// Many implementations are enumerable, allowing all command lines to be
+/// retrieved. These can be used to run clang tools over a subset of the files
+/// in a project.
 class CompilationDatabase {
 public:
   virtual ~CompilationDatabase();
@@ -114,7 +116,10 @@
     StringRef FilePath) const = 0;
 
   /// \brief Returns the list of all files available in the compilation database.
-  virtual std::vector<std::string> getAllFiles() const = 0;
+  ///
+  /// By default, returns nothing. Implementations should override this if they
+  /// can enumerate their source files.
+  virtual std::vector<std::string> getAllFiles() const { return {}; }
 
   /// \brief Returns all compile commands for all the files in the compilation
   /// database.
@@ -122,7 +127,10 @@
   /// FIXME: Add a layer in Tooling that provides an interface to run a tool
   /// over all files in a compilation database. Not all build systems have the
   /// ability to provide a feasible implementation for \c getAllCompileCommands.
-  virtual std::vector<CompileCommand> getAllCompileCommands() const = 0;
+  ///
+  /// By default, this is implemented in terms of getAllFiles() and
+  /// getCompileCommands(). Subclasses may override this for efficiency.
+  virtual std::vector<CompileCommand> getAllCompileCommands() const;
 };
 
 /// \brief Interface for compilation database plugins.
@@ -149,6 +157,7 @@
 /// \brief A compilation database that returns a single compile command line.
 ///
 /// Useful when we want a tool to behave more like a compiler invocation.
+/// This compilation database is not enumerable: getAllFiles() returns {}.
 class FixedCompilationDatabase : public CompilationDatabase {
 public:
   /// \brief Creates a FixedCompilationDatabase from the arguments after "--".
@@ -199,17 +208,6 @@
   std::vector<CompileCommand>
   getCompileCommands(StringRef FilePath) const override;
 
-  /// \brief Returns the list of all files available in the compilation database.
-  ///
-  /// Note: This is always an empty list for the fixed compilation database.
-  std::vector<std::string> getAllFiles() const override;
-
-  /// \brief Returns all compile commands for all the files in the compilation
-  /// database.
-  ///
-  /// Note: This is always an empty list for the fixed compilation database.
-  std::vector<CompileCommand> getAllCompileCommands() const override;
-
 private:
   /// This is built up to contain a single entry vector to be returned from
   /// getCompileCommands after adding the positional argument.
Index: cfe/trunk/lib/Tooling/CompilationDatabase.cpp
===================================================================
--- cfe/trunk/lib/Tooling/CompilationDatabase.cpp
+++ cfe/trunk/lib/Tooling/CompilationDatabase.cpp
@@ -112,6 +112,15 @@
   return DB;
 }
 
+std::vector<CompileCommand> CompilationDatabase::getAllCompileCommands() const {
+  std::vector<CompileCommand> Result;
+  for (const auto &File : getAllFiles()) {
+    auto C = getCompileCommands(File);
+    std::move(C.begin(), C.end(), std::back_inserter(Result));
+  }
+  return Result;
+}
+
 CompilationDatabasePlugin::~CompilationDatabasePlugin() {}
 
 namespace {
@@ -342,16 +351,6 @@
   return Result;
 }
 
-std::vector<std::string>
-FixedCompilationDatabase::getAllFiles() const {
-  return std::vector<std::string>();
-}
-
-std::vector<CompileCommand>
-FixedCompilationDatabase::getAllCompileCommands() const {
-  return std::vector<CompileCommand>();
-}
-
 namespace {
 
 class FixedCompilationDatabasePlugin : public CompilationDatabasePlugin {