fix a potential bug in the c++ reader

paddle/fluid/framework/reader.h

@@ -65,12 +65,25 @@ class ReaderHolder {
 
   ReaderBase* Get() const { return reader_.get(); }
 
-  void ReadNext(std::vector<LoDTensor>* out) { reader_->ReadNext(out); }
-  void ReInit() { reader_->ReInit(); }
+  void ReadNext(std::vector<LoDTensor>* out) {
+    PADDLE_ENFORCE_NOT_NULL(reader_);
+    reader_->ReadNext(out);
+  }
+  void ReInit() {
+    PADDLE_ENFORCE_NOT_NULL(reader_);
+    reader_->ReInit();
+  }
 
-  DDim shape(size_t idx) const { return reader_->shape(idx); }
-  std::vector<DDim> shapes() const { return reader_->shapes(); }
+  DDim shape(size_t idx) const {
+    PADDLE_ENFORCE_NOT_NULL(reader_);
+    return reader_->shape(idx);
+  }
+  std::vector<DDim> shapes() const {
+    PADDLE_ENFORCE_NOT_NULL(reader_);
+    return reader_->shapes();
+  }
   void set_shapes(const std::vector<DDim>& shapes) {
+    PADDLE_ENFORCE_NOT_NULL(reader_);
     reader_->set_shapes(shapes);
   }
 

paddle/fluid/operators/reader/reader_op_registry.cc

@@ -49,6 +49,10 @@ FileReaderMakerBase::FileReaderMakerBase(
 }
 
 void FileReaderInferShape::operator()(framework::InferShapeContext* ctx) const {
+  PADDLE_ENFORCE(
+      !ctx->IsRuntime(),
+      "'FileReaderInferShape' should only be invoked during compile time.");
+
   PADDLE_ENFORCE(ctx->HasOutput("Out"),
                  "The output file reader should not be null.");
   const auto shape_concat = ctx->Attrs().Get<std::vector<int>>("shape_concat");
@@ -56,7 +60,6 @@ void FileReaderInferShape::operator()(framework::InferShapeContext* ctx) const {
   std::vector<framework::DDim> shapes = RestoreShapes(shape_concat, ranks);
   ctx->SetReaderDims("Out", shapes);
 
-  if (ctx->IsRuntime()) {
   const auto lod_levels = ctx->Attrs().Get<std::vector<int>>("lod_levels");
   PADDLE_ENFORCE_EQ(lod_levels.size(), shapes.size(),
                     "The number of 'lod_levels'(%d) doesn't match the number "
@@ -65,7 +68,6 @@ void FileReaderInferShape::operator()(framework::InferShapeContext* ctx) const {
   framework::VarDesc* reader =
       boost::get<framework::VarDesc*>(ctx->GetOutputVarPtrs("Out")[0]);
   reader->SetLoDLevels(lod_levels);
-  }
 }
 
 void FileReaderInferVarType::operator()(const framework::OpDesc& op_desc,
@@ -77,19 +79,21 @@ void FileReaderInferVarType::operator()(const framework::OpDesc& op_desc,
 
 void DecoratedReaderInferShape::operator()(
     framework::InferShapeContext* ctx) const {
+  PADDLE_ENFORCE(!ctx->IsRuntime(),
+                 "'DecoratedReaderInferShape' should only be invoked during "
+                 "compile time.");
+
   PADDLE_ENFORCE(ctx->HasInput("UnderlyingReader"),
                  "Input(UnderlyingReader) should not be null.");
   PADDLE_ENFORCE(ctx->HasOutput("Out"),
                  "The output decorated reader should not be null.");
   ctx->SetReaderDims("Out", ctx->GetReaderDims("UnderlyingReader"));
 
-  if (ctx->IsRuntime()) {
   framework::VarDesc* in_reader = boost::get<framework::VarDesc*>(
       ctx->GetInputVarPtrs("UnderlyingReader")[0]);
   framework::VarDesc* out_reader =
       boost::get<framework::VarDesc*>(ctx->GetOutputVarPtrs("Out")[0]);
   out_reader->SetLoDLevels(in_reader->GetLoDLevels());
-  }
 }
 void DecoratedReaderInferVarType::operator()(
     const framework::OpDesc& op_desc, framework::BlockDesc* block) const {