[PCH] Mark a PCH file with a flag to indicate if the serialized AST had
compiler errors or not.

-Control whether ASTReader should reject such a PCH by a boolean flag at ASTReader's creation time.
By default, such a PCH file will be rejected with an error when trying to load it.

[libclang] Allow clang_saveTranslationUnit to create a PCH file even if compiler errors
occurred.
-Have libclang API calls accept a PCH that had compiler errors.

The general idea is that we want libclang to stay functional even if a PCH had a compiler error.
rdar://10976363.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152192 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 39f24da..5684949 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -1807,6 +1807,12 @@
         return IgnorePCH;
       }
 
+      bool hasErrors = Record[5];
+      if (hasErrors && !DisableValidation && !AllowASTWithCompilerErrors) {
+        Diag(diag::err_pch_with_compiler_errors);
+        return IgnorePCH;
+      }
+
       RelocatablePCH = Record[4];
       if (Listener) {
         std::string TargetTriple(BlobStart, BlobLen);
@@ -6282,14 +6288,15 @@
 
 ASTReader::ASTReader(Preprocessor &PP, ASTContext &Context,
                      StringRef isysroot, bool DisableValidation,
-                     bool DisableStatCache)
+                     bool DisableStatCache, bool AllowASTWithCompilerErrors)
   : Listener(new PCHValidator(PP, *this)), DeserializationListener(0),
     SourceMgr(PP.getSourceManager()), FileMgr(PP.getFileManager()),
     Diags(PP.getDiagnostics()), SemaObj(0), PP(PP), Context(Context),
     Consumer(0), ModuleMgr(FileMgr.getFileSystemOptions()),
     RelocatablePCH(false), isysroot(isysroot),
     DisableValidation(DisableValidation),
-    DisableStatCache(DisableStatCache), 
+    DisableStatCache(DisableStatCache),
+    AllowASTWithCompilerErrors(AllowASTWithCompilerErrors), 
     CurrentGeneration(0), NumStatHits(0), NumStatMisses(0), 
     NumSLocEntriesRead(0), TotalNumSLocEntries(0), 
     NumStatementsRead(0), TotalNumStatements(0), NumMacrosRead(0),