Index: clang-tools-extra/trunk/clang-tidy/ClangTidy.cpp
===================================================================
--- clang-tools-extra/trunk/clang-tidy/ClangTidy.cpp
+++ clang-tools-extra/trunk/clang-tidy/ClangTidy.cpp
@@ -524,6 +524,18 @@
     ActionFactory(ClangTidyContext &Context) : ConsumerFactory(Context) {}
     FrontendAction *create() override { return new Action(&ConsumerFactory); }
 
+    bool runInvocation(std::shared_ptr<CompilerInvocation> Invocation,
+                       FileManager *Files,
+                       std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+                       DiagnosticConsumer *DiagConsumer) override {
+      // Explicitly set ProgramAction to RunAnalysis to make the preprocessor
+      // define __clang_analyzer__ macro. The frontend analyzer action will not
+      // be called here.
+      Invocation->getFrontendOpts().ProgramAction = frontend::RunAnalysis;
+      return FrontendActionFactory::runInvocation(
+          Invocation, Files, PCHContainerOps, DiagConsumer);
+    }
+
   private:
     class Action : public ASTFrontendAction {
     public:
Index: clang-tools-extra/trunk/test/clang-tidy/clang-tidy-__clang_analyzer__macro.cpp
===================================================================
--- clang-tools-extra/trunk/test/clang-tidy/clang-tidy-__clang_analyzer__macro.cpp
+++ clang-tools-extra/trunk/test/clang-tidy/clang-tidy-__clang_analyzer__macro.cpp
@@ -0,0 +1,10 @@
+// RUN: clang-tidy %s -checks=-*,modernize-use-nullptr -- | count 0
+
+#if !defined(__clang_analyzer__)
+#error __clang_analyzer__ is not defined
+#endif
+// RUN: clang-tidy %s -checks=-*,modernize-use-nullptr -- | count 0
+
+#if !defined(__clang_analyzer__)
+#error __clang_analyzer__ is not defined
+#endif