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

Author: jmmartinez

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().SetMacroExpansionOnlyInDirectives();
     return true;
   }
 
@@ -98,7 +100,11 @@ class FrontendAction {
   ///
   /// This is guaranteed to only be called following a successful call to
   /// BeginSourceFileAction (and BeginSourceFile).
-  virtual void EndSourceFileAction() {}
+  virtual void EndSourceFileAction() {
+    if (CurrentInput.isPreprocessed())
+      // Reset the preprocessor macro expansion to the default.
+      getCompilerInstance().getPreprocessor().SetEnableMacroExpansion();
+  }
 
   /// Callback at the end of processing a single input, to determine
   /// if the output files should be erased or not.

clang/include/clang/Lex/Preprocessor.h

@@ -1847,6 +1847,10 @@ class Preprocessor {
     MacroExpansionInDirectivesOverride = true;
   }
 
+  void SetEnableMacroExpansion() {
+    DisableMacroExpansion = MacroExpansionInDirectivesOverride = false;
+  }
+
   /// Peeks ahead N tokens and returns that token without consuming any
   /// tokens.
   ///

clang/lib/CodeGen/CodeGenAction.cpp

@@ -908,6 +908,8 @@ bool CodeGenAction::loadLinkModules(CompilerInstance &CI) {
 bool CodeGenAction::hasIRSupport() const { return true; }
 
 void CodeGenAction::EndSourceFileAction() {
+  ASTFrontendAction::EndSourceFileAction();
+
   // If the consumer creation failed, do nothing.
   if (!getCompilerInstance().hasASTConsumer())
     return;
@@ -932,7 +934,7 @@ CodeGenerator *CodeGenAction::getCodeGenerator() const {
 bool CodeGenAction::BeginSourceFileAction(CompilerInstance &CI) {
   if (CI.getFrontendOpts().GenReducedBMI)
     CI.getLangOpts().setCompilingModule(LangOptions::CMK_ModuleInterface);
-  return true;
+  return ASTFrontendAction::BeginSourceFileAction(CI);
 }
 
 static std::unique_ptr<raw_pwrite_stream>

clang/lib/Frontend/FrontendActions.cpp

@@ -181,7 +181,7 @@ bool GeneratePCHAction::shouldEraseOutputFiles() {
 
 bool GeneratePCHAction::BeginSourceFileAction(CompilerInstance &CI) {
   CI.getLangOpts().CompilingPCH = true;
-  return true;
+  return ASTFrontendAction::BeginSourceFileAction(CI);
 }
 
 std::vector<std::unique_ptr<ASTConsumer>>

clang/lib/Frontend/Rewrite/FrontendActions.cpp

@@ -103,12 +103,13 @@ bool FixItAction::BeginSourceFileAction(CompilerInstance &CI) {
   }
   Rewriter.reset(new FixItRewriter(CI.getDiagnostics(), CI.getSourceManager(),
                                    CI.getLangOpts(), FixItOpts.get()));
-  return true;
+  return ASTFrontendAction::BeginSourceFileAction(CI);
 }
 
 void FixItAction::EndSourceFileAction() {
   // Otherwise rewrite all files.
   Rewriter->WriteFixedFiles();
+  ASTFrontendAction::EndSourceFileAction();
 }
 
 bool FixItRecompile::BeginInvocation(CompilerInstance &CI) {
@@ -298,7 +299,7 @@ bool RewriteIncludesAction::BeginSourceFileAction(CompilerInstance &CI) {
         std::make_unique<RewriteImportsListener>(CI, OutputStream));
   }
 
-  return true;
+  return PreprocessorFrontendAction::BeginSourceFileAction(CI);
 }
 
 void RewriteIncludesAction::ExecuteAction() {

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

@@ -1,7 +1,8 @@
 // RUN: %clang_cc1 -E -x c %s | FileCheck %s --check-prefixes=EXPANDED
-// RUN: %clang_cc1 -E -x cpp-output %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() {