Don't allow multiple symbol tables in the module block.

src/PNaClTranslator.cpp

 //===- subzero/src/PNaClTranslator.cpp - ICE from bitcode -----------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 2932 matching lines @@
 
   ~ModuleParser() override = default;
 
   const char *getBlockName() const override { return "module"; }
 
 private:
   Ice::TimerMarker Timer;
   // True if we have already installed names for unnamed global declarations,
   // and have generated global constant initializers.
   bool GlobalDeclarationNamesAndInitializersInstalled = false;
+  // True if we have already processed the symbol table for the module.
+  bool FoundValuesymtab = false;
 
   // Generates names for unnamed global addresses (i.e. functions and global
   // variables). Then lowers global variable declaration initializers to the
   // target. May be called multiple times. Only the first call will do the
   // installation.
   void installGlobalNamesAndGlobalVarInitializers() {
     if (!GlobalDeclarationNamesAndInitializersInstalled) {
       Context->installGlobalNames();
       Context->createValueIDs();
-      getTranslator().lowerGlobals(Context->getGlobalVariables());
+      std::unique_ptr<Ice::VariableDeclarationList> Globals =
+          Context->getGlobalVariables();
+      if (Globals)
+        getTranslator().lowerGlobals(std::move(Globals));
       GlobalDeclarationNamesAndInitializersInstalled = true;
     }
   }
   bool ParseBlock(unsigned BlockID) override;
 
   void ExitBlock() override { installGlobalNamesAndGlobalVarInitializers(); }
 
   void ProcessRecord() override;
 };
 
@@ skipping 37 matching lines @@
     return NaClBitcodeParser::ParseBlock(BlockID);
   case naclbitc::TYPE_BLOCK_ID_NEW: {
     TypesParser Parser(BlockID, this);
     return Parser.ParseThisBlock();
   }
   case naclbitc::GLOBALVAR_BLOCK_ID: {
     GlobalsParser Parser(BlockID, this);
     return Parser.ParseThisBlock();
   }
   case naclbitc::VALUE_SYMTAB_BLOCK_ID: {
+    if (FoundValuesymtab)
+      Fatal("Duplicate valuesymtab in module");
+
+    FoundValuesymtab = true;
     ModuleValuesymtabParser Parser(BlockID, this);
     return Parser.ParseThisBlock();
   }
   case naclbitc::FUNCTION_BLOCK_ID: {
     installGlobalNamesAndGlobalVarInitializers();
     FunctionParser Parser(BlockID, this);
     return Parser.convertFunction();
   }
   default:
     return BlockParserBaseClass::ParseBlock(BlockID);
@@ skipping 116 matching lines @@
   }
   if (InputStreamFile.getBitcodeBytes().getExtent() % 4 != 0) {
     ErrStream
         << IRFilename
         << ": Bitcode stream should be a multiple of 4 bytes in length.\n";
     llvm::report_fatal_error("Bitcode stream should be a multiple of 4 bytes");
   }
 }
 
 } // end of namespace Ice