[Frontend] Fix printing policy for AST context loaded from file

In ASTUnit::LoadFromASTFile, the context object is set up using
default-constructed LangOptions (which only later get populated). As the
language options are used in the constructor of PrintingPolicy, this
needs to be updated explicitly after the language options are available.

Patch by Johann Klähn!

Differential Revision: https://reviews.llvm.org/D35271

llvm-svn: 311787

clang/lib/Frontend/ASTUnit.cpp

@@ -542,6 +542,9 @@ private:
     // Initialize the ASTContext
     Context->InitBuiltinTypes(*Target);
 
+    // Adjust printing policy based on language options.
+    Context->setPrintingPolicy(PrintingPolicy(LangOpt));
+
     // We didn't have access to the comment options when the ASTContext was
     // constructed, so register them now.
     Context->getCommentCommandTraits().registerCommentOptions(

clang/unittests/Frontend/ASTUnitTest.cpp

@@ -0,0 +1,87 @@
+//===- unittests/Frontend/ASTUnitTest.cpp - ASTUnit tests -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include <fstream>
+
+#include "clang/Frontend/ASTUnit.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/CompilerInvocation.h"
+#include "clang/Frontend/PCHContainerOperations.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace clang;
+
+namespace {
+
+TEST(ASTUnit, SaveLoadPreservesLangOptionsInPrintingPolicy) {
+  // Check that the printing policy is restored with the correct language
+  // options when loading an ASTUnit from a file.  To this end, an ASTUnit
+  // for a C++ translation unit is set up and written to a temporary file.
+
+  // By default `UseVoidForZeroParams` is true for non-C++ language options,
+  // thus we can check this field after loading the ASTUnit to deduce whether
+  // the correct (C++) language options were used when setting up the printing
+  // policy.
+
+  {
+    PrintingPolicy PolicyWithDefaultLangOpt(LangOptions{});
+    EXPECT_TRUE(PolicyWithDefaultLangOpt.UseVoidForZeroParams);
+  }
+
+  int FD;
+  llvm::SmallString<256> InputFileName;
+  ASSERT_FALSE(llvm::sys::fs::createTemporaryFile("ast-unit", "cpp", FD, InputFileName));
+  tool_output_file input_file(InputFileName, FD);
+  input_file.os() << "";
+
+  const char* Args[] = {"clang", "-xc++", InputFileName.c_str()};
+
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+      CompilerInstance::createDiagnostics(new DiagnosticOptions());
+
+  std::shared_ptr<CompilerInvocation> CInvok =
+      createInvocationFromCommandLine(Args, Diags);
+
+  if (!CInvok)
+    FAIL() << "could not create compiler invocation";
+
+  FileManager *FileMgr =
+      new FileManager(FileSystemOptions(), vfs::getRealFileSystem());
+  auto PCHContainerOps = std::make_shared<PCHContainerOperations>();
+
+  std::unique_ptr<ASTUnit> AST = ASTUnit::LoadFromCompilerInvocation(
+      CInvok, PCHContainerOps, Diags, FileMgr);
+
+  if (!AST)
+    FAIL() << "failed to create ASTUnit";
+
+  EXPECT_FALSE(AST->getASTContext().getPrintingPolicy().UseVoidForZeroParams);
+
+  llvm::SmallString<256> ASTFileName;
+  ASSERT_FALSE(llvm::sys::fs::createTemporaryFile("ast-unit", "ast", FD, ASTFileName));
+  tool_output_file ast_file(ASTFileName, FD);
+  AST->Save(ASTFileName.str());
+
+  EXPECT_TRUE(llvm::sys::fs::exists(ASTFileName));
+
+  std::unique_ptr<ASTUnit> AU = ASTUnit::LoadFromASTFile(
+      ASTFileName.str(), PCHContainerOps->getRawReader(), ASTUnit::LoadEverything, Diags,
+      FileSystemOptions(), /*UseDebugInfo=*/false);
+
+  if (!AU)
+    FAIL() << "failed to load ASTUnit";
+
+  EXPECT_FALSE(AU->getASTContext().getPrintingPolicy().UseVoidForZeroParams);
+}
+
+} // anonymous namespace

clang/unittests/Frontend/CMakeLists.txt

@@ -3,6 +3,7 @@ set(LLVM_LINK_COMPONENTS
   )
 
 add_clang_unittest(FrontendTests
+  ASTUnitTest.cpp
   FrontendActionTest.cpp
   CodeGenActionTest.cpp
   )