namespace tensorflow {
namespace checkpoint {

class TensorSliceReader;

CheckpointReader::CheckpointReader(const string& filename, TF_Status* status)
    : reader_(nullptr),
      v2_reader_(nullptr),
      var_to_shape_map_(nullptr),
      var_to_data_type_map_(nullptr) {
  // Depending on whether this is a V2 ckpt, initializes "reader_" or
  // "v2_reader_".
  std::vector<string> v2_path;

  if (!s.ok()) {
    return nullptr;
  }
  s = op->AddInputList(gradient_tensors);
  if (!s.ok()) {
    return nullptr;
  }

  int num_outputs = 1;
  std::vector<AbstractTensorHandle*> outputs(num_outputs);
  s = op->Execute(absl::Span<AbstractTensorHandle*>(outputs), &num_outputs);
  if (!s.ok()) {
    return nullptr;
  }
  return outputs[0];
}

*   Fixes an undefined behavior arising from reference binding to nullptr in
    `RaggedTensorToSparse`
    ([CVE-2021-37656](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-37656))
*   Fixes an undefined behavior arising from reference binding to nullptr in
    `MatrixDiagV*` ops
    ([CVE-2021-37657](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-37657))