Shut up warnings (#1363)

* Shut up warnings

- warning: 'void* memset(void*, int, size_t)' clearing an object of non-trivial type 'struct LightGBM::HistogramBinEntry'; use assignment or value-initialization instead [-Wclass-memaccess]
- warning: 'void* memcpy(void*, const void*, size_t)' writing to an object of type 'class std::tuple<int, double, double>' with no trivial copy-assignment; use copy-assignment or copy-initialization instead [-Wclass-memaccess]

* void*

src/io/dataset.cpp

@@ -658,7 +658,7 @@ void Dataset::ConstructHistograms(const std::vector<int8_t>& is_feature_used,
         // feature is not used
         auto data_ptr = hist_data + group_bin_boundaries_[group];
         const int num_bin = feature_groups_[group]->num_total_bin_;
-        std::memset(data_ptr + 1, 0, (num_bin - 1) * sizeof(HistogramBinEntry));
+        std::memset((void*)(data_ptr + 1), 0, (num_bin - 1) * sizeof(HistogramBinEntry));
         // construct histograms for smaller leaf
         if (ordered_bins[group] == nullptr) {
           // if not use ordered bin
@@ -687,7 +687,7 @@ void Dataset::ConstructHistograms(const std::vector<int8_t>& is_feature_used,
         // feature is not used
         auto data_ptr = hist_data + group_bin_boundaries_[group];
         const int num_bin = feature_groups_[group]->num_total_bin_;
-        std::memset(data_ptr + 1, 0, (num_bin - 1) * sizeof(HistogramBinEntry));
+        std::memset((void*)(data_ptr + 1), 0, (num_bin - 1) * sizeof(HistogramBinEntry));
         // construct histograms for smaller leaf
         if (ordered_bins[group] == nullptr) {
           // if not use ordered bin
@@ -720,7 +720,7 @@ void Dataset::ConstructHistograms(const std::vector<int8_t>& is_feature_used,
         // feature is not used
         auto data_ptr = hist_data + group_bin_boundaries_[group];
         const int num_bin = feature_groups_[group]->num_total_bin_;
-        std::memset(data_ptr + 1, 0, (num_bin - 1) * sizeof(HistogramBinEntry));
+        std::memset((void*)(data_ptr + 1), 0, (num_bin - 1) * sizeof(HistogramBinEntry));
         // construct histograms for smaller leaf
         if (ordered_bins[group] == nullptr) {
           // if not use ordered bin
@@ -748,7 +748,7 @@ void Dataset::ConstructHistograms(const std::vector<int8_t>& is_feature_used,
         // feature is not used
         auto data_ptr = hist_data + group_bin_boundaries_[group];
         const int num_bin = feature_groups_[group]->num_total_bin_;
-        std::memset(data_ptr + 1, 0, (num_bin - 1) * sizeof(HistogramBinEntry));
+        std::memset((void*)(data_ptr + 1), 0, (num_bin - 1) * sizeof(HistogramBinEntry));
         // construct histograms for smaller leaf
         if (ordered_bins[group] == nullptr) {
           // if not use ordered bin

src/treelearner/data_parallel_tree_learner.cpp

@@ -136,7 +136,7 @@ void DataParallelTreeLearner<TREELEARNER_T>::BeforeTrain() {
     }
   });
   // copy back
-  std::memcpy(&data, output_buffer_.data(), size);
+  std::memcpy((void*)&data, output_buffer_.data(), size);
   // set global sumup info
   this->smaller_leaf_splits_->Init(std::get<1>(data), std::get<2>(data));
   // init global data count in leaf

src/treelearner/voting_parallel_tree_learner.cpp

@@ -131,7 +131,7 @@ void VotingParallelTreeLearner<TREELEARNER_T>::BeforeTrain() {
     }
   });
 
-  std::memcpy(&data, output_buffer_.data(), size);
+  std::memcpy((void*)&data, output_buffer_.data(), size);
 
   // set global sumup info
   smaller_leaf_splits_global_->Init(std::get<1>(data), std::get<2>(data));