[clang] Fix an uint32_t overflow in large preamble.

[hokein]

Summary

I was surprised to see the LocalOffset can exceed uint32_t, but it
does happen and lead to crashes in one of our internal huge TU with a large
preamble.

with this patch, the crash is gone.

[sammccall]

Thanks for tracking this down!

clang/include/clang/Serialization/ASTReader.h

private:
   RecordLocation DeclCursorForID(serialization::DeclID ID,
                                  SourceLocation &Location);
   void loadDeclUpdateRecords(PendingUpdateRecord &Record);
   void loadPendingDeclChain(Decl *D, uint64_t LocalOffset);
   void loadObjCCategories(serialization::GlobalDeclID ID, ObjCInterfaceDecl *D,
                           unsigned PreviousGeneration = 0);
 
   RecordLocation getLocalBitOffset(uint64_t GlobalOffset);
-  uint64_t getGlobalBitOffset(ModuleFile &M, uint32_t LocalOffset);
+  uint64_t getGlobalBitOffset(ModuleFile &M, uint64_t LocalOffset);
 
   /// Returns the first preprocessed entity ID that begins or ends after
   /// \arg Loc.
   serialization::PreprocessedEntityID
   findPreprocessedEntity(SourceLocation Loc, bool EndsAfter) const;
 
   /// Find the next module that contains entities and return the ID
   /// of the first entry.

clang/include/clang/Serialization/ASTRecordReader.h

return ExplicitSpecifier(HasExpr ? readExpr() : nullptr,
                              static_cast<ExplicitSpecKind>(Kind));
   }
 
   /// Read information about an exception specification (inherited).
   //FunctionProtoType::ExceptionSpecInfo
   //readExceptionSpecInfo(SmallVectorImpl<QualType> &ExceptionStorage);
 
   /// Get the global offset corresponding to a local offset.
-  uint64_t getGlobalBitOffset(uint32_t LocalOffset) {
+  uint64_t getGlobalBitOffset(uint64_t LocalOffset) {
     return Reader->getGlobalBitOffset(*F, LocalOffset);
   }
 
   /// Reads a statement.
   Stmt *readStmt() { return Reader->ReadStmt(*F); }
   Stmt *readStmtRef() { return readStmt(); /* FIXME: readSubStmt? */ }
 
   /// Reads an expression.

clang/lib/Serialization/ASTReaderDecl.cpp

 
 ASTReader::RecordLocation ASTReader::getLocalBitOffset(uint64_t GlobalOffset) {
   auto I = GlobalBitOffsetsMap.find(GlobalOffset);
 
   assert(I != GlobalBitOffsetsMap.end() && "Corrupted global bit offsets map");
   return RecordLocation(I->second, GlobalOffset - I->second->GlobalBitOffset);
 }
 
-uint64_t ASTReader::getGlobalBitOffset(ModuleFile &M, uint32_t LocalOffset) {
+uint64_t ASTReader::getGlobalBitOffset(ModuleFile &M, uint64_t LocalOffset) {
   return LocalOffset + M.GlobalBitOffset;
 }
 
 static bool isSameTemplateParameterList(const ASTContext &C,
                                         const TemplateParameterList *X,
                                         const TemplateParameterList *Y);
 
 /// Determine whether two template parameters are similar enough