[Preprocessor] Do not expand macros if the input is already preprocessed

clang/include/clang/Frontend/FrontendAction.h

@@ -84,6 +84,8 @@ class FrontendAction {
   /// \return True on success; on failure ExecutionAction() and
   /// EndSourceFileAction() will not be called.
   virtual bool BeginSourceFileAction(CompilerInstance &CI) {
+    if (CurrentInput.isPreprocessed())
+      CI.getPreprocessor().SetDisableMacroExpansion();
     return true;
   }
 

clang/include/clang/Lex/Preprocessor.h

@@ -1831,6 +1831,11 @@ class Preprocessor {
     MacroExpansionInDirectivesOverride = true;
   }
 
+  void SetDisableMacroExpansion() {
+    DisableMacroExpansion = true;
+    MacroExpansionInDirectivesOverride = false;
+  }
+
   /// Peeks ahead N tokens and returns that token without consuming any
   /// tokens.
   ///

clang/lib/Frontend/InitPreprocessor.cpp

@@ -1558,6 +1558,7 @@ void clang::InitializePreprocessor(Preprocessor &PP,
                                    const PCHContainerReader &PCHContainerRdr,
                                    const FrontendOptions &FEOpts,
                                    const CodeGenOptions &CodeGenOpts) {
+
   const LangOptions &LangOpts = PP.getLangOpts();
   std::string PredefineBuffer;
   PredefineBuffer.reserve(4080);

clang/test/Modules/initializers.cpp

@@ -48,6 +48,7 @@
 // instantiation for v<int> in one of the two headers, because we will only
 // parse one of the two get() functions.
 
+#ifdef NS
 #pragma clang module build m
 module m {
   module a {
@@ -60,9 +61,7 @@ module m {
 #pragma clang module begin m.a
 inline int non_trivial() { return 3; }
 
-#ifdef NS
 namespace ns {
-#endif
 
 int a = non_trivial();
 inline int b = non_trivial();
@@ -102,12 +101,64 @@ inline void use(bool b, ...) {
       X<int>::e<int>, X<int>::f<int>, X<int>::g<int>, X<int>::h<int>);
 }
 
-#ifdef NS
 }
-#endif
 
 #pragma clang module end
 #pragma clang module endbuild
+#else
+#pragma clang module build m
+module m {
+  module a {
+    header "foo.h" { size 123 mtime 456789 }
+  }
+  module b {}
+}
+
+#pragma clang module contents
+#pragma clang module begin m.a
+inline int non_trivial() { return 3; }
+
+int a = non_trivial();
+inline int b = non_trivial();
+thread_local int c = non_trivial();
+inline thread_local int d = non_trivial();
+
+template<typename U> int e = non_trivial();
+template<typename U> inline int f = non_trivial();
+template<typename U> thread_local int g = non_trivial();
+template<typename U> inline thread_local int h = non_trivial();
+
+inline int unused = 123; // should not be emitted
+
+template<typename T> struct X {
+  static int a;
+  static inline int b = non_trivial();
+  static thread_local int c;
+  static inline thread_local int d = non_trivial();
+
+  template<typename U> static int e;
+  template<typename U> static inline int f = non_trivial();
+  template<typename U> static thread_local int g;
+  template<typename U> static inline thread_local int h = non_trivial();
+
+  static inline int unused = 123; // should not be emitted
+};
+
+template<typename T> int X<T>::a = non_trivial();
+template<typename T> thread_local int X<T>::c = non_trivial();
+template<typename T> template<typename U> int X<T>::e = non_trivial();
+template<typename T> template<typename U> thread_local int X<T>::g = non_trivial();
+
+inline void use(bool b, ...) {
+  if (b) return;
+  use(true, e<int>, f<int>, g<int>, h<int>,
+      X<int>::a, X<int>::b, X<int>::c, X<int>::d,
+      X<int>::e<int>, X<int>::f<int>, X<int>::g<int>, X<int>::h<int>);
+}
+
+#pragma clang module end
+#pragma clang module endbuild
+#endif
 
 #if IMPORT == 1
 // Import the module and the m.a submodule; runs the ordered initializers and

clang/test/Preprocessor/preprocess-cpp-output.c

@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -E -x c %s | FileCheck %s --check-prefixes=EXPANDED
+// RUN: %clang_cc1 -E -x cpp-output %s | FileCheck %s --check-prefixes=NOT-EXPANDED
+
+// EXPANDED: void __attribute__((__attribute__((always_inline)))) foo()
+// NOT-EXPANDED: void __attribute__((always_inline)) foo()
+
+#define always_inline __attribute__((always_inline))
+void __attribute__((always_inline)) foo() {
+    return 4;
+}