add nullptr check for get_field

include/LightGBM/dataset.h

@@ -143,8 +143,13 @@ public:
   * \brief Get weights, if not exists, will return nullptr
   * \return Pointer of weights
   */
-  inline const float* weights()
-            const { return weights_.data(); }
+  inline const float* weights() const {
+    if (weights_.size() > 0) {
+      return weights_.data();
+    } else {
+      return nullptr;
+    }
+  }
 
   /*!
   * \brief Get data boundaries on queries, if not exists, will return nullptr
@@ -153,8 +158,13 @@ public:
   *        is the data indices for query i.
   * \return Pointer of data boundaries on queries
   */
-  inline const data_size_t* query_boundaries()
-           const { return query_boundaries_.data(); }
+  inline const data_size_t* query_boundaries() const { 
+    if (query_boundaries_.size() > 0) {
+      return query_boundaries_.data();
+    } else {
+      return nullptr;
+    }
+  }
 
   /*!
   * \brief Get Number of queries
@@ -166,13 +176,25 @@ public:
   * \brief Get weights for queries, if not exists, will return nullptr
   * \return Pointer of weights for queries
   */
-  inline const float* query_weights() const { return query_weights_.data(); }
+  inline const float* query_weights() const { 
+    if (query_weights_.size() > 0) {
+      return query_weights_.data();
+    } else {
+      return nullptr;
+    }
+  }
 
   /*!
   * \brief Get initial scores, if not exists, will return nullptr
   * \return Pointer of initial scores
   */
-  inline const float* init_score() const { return init_score_.data(); }
+  inline const float* init_score() const { 
+    if (init_score_.size() > 0) {
+      return init_score_.data();
+    } else {
+      return nullptr;
+    }
+  }
 
   /*! \brief Disable copy */
   Metadata& operator=(const Metadata&) = delete;

src/c_api.cpp

@@ -387,7 +387,7 @@ DllExport int LGBM_DatasetGetField(DatesetHandle handle,
     *out_type = C_API_DTYPE_INT32;
     is_success = true;
   }
-  if (!is_success) { throw std::runtime_error("Field not found"); }
+  if (!is_success) { throw std::runtime_error("Field not found or not exist"); }
   API_END();
 }
 

src/io/dataset.cpp

@@ -101,7 +101,11 @@ bool Dataset::GetFloatField(const char* field_name, int64_t* out_len, const floa
   } else {
     return false;
   }
+  if (*out_ptr != nullptr) {
     return true;
+  } else {
+    return false;
+  }
 }
 
 bool Dataset::GetIntField(const char* field_name, int64_t* out_len, const int** out_ptr) {
@@ -109,11 +113,15 @@ bool Dataset::GetIntField(const char* field_name, int64_t* out_len, const int**
   name = Common::Trim(name);
   if (name == std::string("query") || name == std::string("group")) {
     *out_ptr = metadata_.query_boundaries();
-    *out_len = num_data_;
+    *out_len = metadata_.num_queries();
   } else {
     return false;
   }
+  if (*out_ptr != nullptr) {
     return true;
+  } else {
+    return false;
+  }
 }
 
 void Dataset::SaveBinaryFile(const char* bin_filename) {