Compiler warnings with VS 2015

[StrikerRUS]

There are a lot of warnings produced by VS 2015:

C:\Users\ntitov\Downloads\LightGBM\build>cmake -A x64 ..
-- Building for: Visual Studio 14 2015
-- Selecting Windows SDK version 10.0.10586.0 to target Windows 10.0.14393.
-- The C compiler identification is MSVC 19.0.24215.1
-- The CXX compiler identification is MSVC 19.0.24215.1
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/x86_amd64/cl.exe
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/x86_amd64/cl.exe - works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/x86_amd64/cl.exe
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/x86_amd64/cl.exe - works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found OpenMP_C: -openmp (found version "2.0")
-- Found OpenMP_CXX: -openmp (found version "2.0")
-- Found OpenMP: TRUE (found version "2.0")
-- Performing Test MM_PREFETCH
-- Performing Test MM_PREFETCH - Failed
-- Performing Test MM_MALLOC
-- Performing Test MM_MALLOC - Failed
-- Configuring done
-- Generating done
-- Build files have been written to: C:/Users/ntitov/Downloads/LightGBM/build

C:\Users\ntitov\Downloads\LightGBM\build>cmake --build . --target ALL_BUILD --config Release
Microsoft (R) Build Engine version 14.0.25420.1
Copyright (C) Microsoft Corporation. All rights reserved.

  Checking Build System
  Building Custom Rule C:/Users/ntitov/Downloads/LightGBM/CMakeLists.txt
  application.cpp
  boosting.cpp
  gbdt.cpp
  gbdt_model_text.cpp
  gbdt_prediction.cpp
  prediction_early_stop.cpp
  bin.cpp
  config.cpp
  config_auto.cpp
  dataset.cpp
  dataset_loader.cpp
  file_io.cpp
  json11.cpp
c:\users\ntitov\downloads\lightgbm\src\boosting\prediction_early_stop.cpp(88): warning C4702: unreachable code [C:\User
s\ntitov\Downloads\LightGBM\build\_lightgbm.vcxproj]
  metadata.cpp
C:\Users\ntitov\Downloads\LightGBM\src\io\dataset.cpp(380): warning C4800: 'signed char': forcing value to bool 'true'
or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\_lightgbm.vcxproj]
c:\users\ntitov\downloads\lightgbm\src\io\sparse_bin.hpp(355): warning C4100: 'max_bin': unreferenced formal parameter
(compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp) [C:\Users\ntitov\Downloads\LightGBM\build\_li
ghtgbm.vcxproj]
  c:\users\ntitov\downloads\lightgbm\src\io\sparse_bin.hpp(407): note: see reference to function template instantiation
   'LightGBM::data_size_t LightGBM::SparseBin<uint32_t>::SplitCategoricalInner<false>(uint32_t,uint32_t,uint32_t,const
  uint32_t *,int,const LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t *) c
  onst' being compiled (compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  c:\users\ntitov\downloads\lightgbm\src\io\sparse_bin.hpp(405): note: see reference to function template instantiation
   'LightGBM::data_size_t LightGBM::SparseBin<uint32_t>::SplitCategoricalInner<false>(uint32_t,uint32_t,uint32_t,const
  uint32_t *,int,const LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t *) c
  onst' being compiled (compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  c:\users\ntitov\downloads\lightgbm\src\io\sparse_bin.hpp(404): note: while compiling class template member function '
  LightGBM::data_size_t LightGBM::SparseBin<uint32_t>::SplitCategorical(uint32_t,uint32_t,const uint32_t *,int,const Li
  ghtGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t *) const' (compiling source
   file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp(629): note: see reference to class template instantiation 'LightGBM
  ::SparseBin<uint32_t>' being compiled
c:\users\ntitov\downloads\lightgbm\src\io\dense_bin.hpp(310): warning C4100: 'max_bin': unreferenced formal parameter (
compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp) [C:\Users\ntitov\Downloads\LightGBM\build\_lig
htgbm.vcxproj]
  c:\users\ntitov\downloads\lightgbm\src\io\dense_bin.hpp(362): note: see reference to function template instantiation
  'LightGBM::data_size_t LightGBM::DenseBin<uint32_t,false>::SplitCategoricalInner<false>(uint32_t,uint32_t,uint32_t,co
  nst uint32_t *,int,const LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t
  *) const' being compiled (compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  c:\users\ntitov\downloads\lightgbm\src\io\dense_bin.hpp(360): note: see reference to function template instantiation
  'LightGBM::data_size_t LightGBM::DenseBin<uint32_t,false>::SplitCategoricalInner<false>(uint32_t,uint32_t,uint32_t,co
  nst uint32_t *,int,const LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t
  *) const' being compiled (compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  c:\users\ntitov\downloads\lightgbm\src\io\dense_bin.hpp(359): note: while compiling class template member function 'L
  ightGBM::data_size_t LightGBM::DenseBin<uint32_t,false>::SplitCategorical(uint32_t,uint32_t,const uint32_t *,int,cons
  t LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t *) const' (compiling so
  urce file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp(625): note: see reference to class template instantiation 'LightGBM
  ::DenseBin<uint32_t,false>' being compiled
  parser.cpp
  tree.cpp
  dcg_calculator.cpp
  metric.cpp
  linker_topo.cpp
  linkers_mpi.cpp
  linkers_socket.cpp
  network.cpp
  objective_function.cpp
  data_parallel_tree_learner.cpp
  feature_parallel_tree_learner.cpp
  gpu_tree_learner.cpp
  serial_tree_learner.cpp
  tree_learner.cpp
  voting_parallel_tree_learner.cpp
  c_api.cpp
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\serial_tree_learner.cpp(388): warning C4800: 'signed char': forcing
value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\_lightgbm.vcxproj]
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\serial_tree_learner.cpp(410): warning C4800: 'signed char': forcing
value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\_lightgbm.vcxproj]
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(203): warning C4800: 'signed char': f
orcing value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\_lightgbm.vcxpro
j]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(176): note: while compiling class t
  emplate member function 'void LightGBM::DataParallelTreeLearner<LightGBM::GPUTreeLearner>::FindBestSplitsFromHistogra
  ms(const std::vector<int8_t,std::allocator<_Ty>> &,bool,const LightGBM::Tree *)'
          with
          [
              _Ty=int8_t
          ]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(171): note: see reference to functi
  on template instantiation 'void LightGBM::DataParallelTreeLearner<LightGBM::GPUTreeLearner>::FindBestSplitsFromHistog
  rams(const std::vector<int8_t,std::allocator<_Ty>> &,bool,const LightGBM::Tree *)' being compiled
          with
          [
              _Ty=int8_t
          ]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(259): note: see reference to class
  template instantiation 'LightGBM::DataParallelTreeLearner<LightGBM::GPUTreeLearner>' being compiled
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(217): warning C4800: 'signed char': f
orcing value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\_lightgbm.vcxpro
j]
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(378): warning C4800: 'signed char':
 forcing value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\_lightgbm.vcxp
roj]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(350): note: while compiling class
   template member function 'void LightGBM::VotingParallelTreeLearner<LightGBM::GPUTreeLearner>::FindBestSplitsFromHist
  ograms(const std::vector<int8_t,std::allocator<_Ty>> &,bool,const LightGBM::Tree *)'
          with
          [
              _Ty=int8_t
          ]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(346): note: see reference to func
  tion template instantiation 'void LightGBM::VotingParallelTreeLearner<LightGBM::GPUTreeLearner>::FindBestSplitsFromHi
  stograms(const std::vector<int8_t,std::allocator<_Ty>> &,bool,const LightGBM::Tree *)' being compiled
          with
          [
              _Ty=int8_t
          ]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(457): note: see reference to clas
  s template instantiation 'LightGBM::VotingParallelTreeLearner<LightGBM::GPUTreeLearner>' being compiled
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(394): warning C4800: 'signed char':
 forcing value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\_lightgbm.vcxp
roj]
c:\users\ntitov\downloads\lightgbm\src\objective\objective_function.cpp(52): warning C4702: unreachable code [C:\Users\
ntitov\Downloads\LightGBM\build\_lightgbm.vcxproj]
c:\users\ntitov\downloads\lightgbm\src\c_api.cpp(879): warning C4702: unreachable code [C:\Users\ntitov\Downloads\Light
GBM\build\_lightgbm.vcxproj]
c:\users\ntitov\downloads\lightgbm\src\treelearner\serial_tree_learner.cpp(233): warning C4702: unreachable code [C:\Us
ers\ntitov\Downloads\LightGBM\build\_lightgbm.vcxproj]
     Creating library C:/Users/ntitov/Downloads/LightGBM/Release/lib_lightgbm.lib and object C:/Users/ntitov/Downloads/
  LightGBM/Release/lib_lightgbm.exp
  _lightgbm.vcxproj -> C:\Users\ntitov\Downloads\LightGBM\Release\lib_lightgbm.dll
  Building Custom Rule C:/Users/ntitov/Downloads/LightGBM/CMakeLists.txt
  main.cpp
  application.cpp
  boosting.cpp
  gbdt.cpp
  gbdt_model_text.cpp
  gbdt_prediction.cpp
  prediction_early_stop.cpp
  bin.cpp
  config.cpp
  config_auto.cpp
  dataset.cpp
  dataset_loader.cpp
C:\Users\ntitov\Downloads\LightGBM\src\io\dataset.cpp(380): warning C4800: 'signed char': forcing value to bool 'true'
or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\lightgbm.vcxproj]
c:\users\ntitov\downloads\lightgbm\src\boosting\prediction_early_stop.cpp(88): warning C4702: unreachable code [C:\User
s\ntitov\Downloads\LightGBM\build\lightgbm.vcxproj]
  file_io.cpp
c:\users\ntitov\downloads\lightgbm\src\io\sparse_bin.hpp(355): warning C4100: 'max_bin': unreferenced formal parameter
(compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp) [C:\Users\ntitov\Downloads\LightGBM\build\lig
htgbm.vcxproj]
  c:\users\ntitov\downloads\lightgbm\src\io\sparse_bin.hpp(407): note: see reference to function template instantiation
   'LightGBM::data_size_t LightGBM::SparseBin<uint32_t>::SplitCategoricalInner<false>(uint32_t,uint32_t,uint32_t,const
  uint32_t *,int,const LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t *) c
  onst' being compiled (compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  c:\users\ntitov\downloads\lightgbm\src\io\sparse_bin.hpp(405): note: see reference to function template instantiation
   'LightGBM::data_size_t LightGBM::SparseBin<uint32_t>::SplitCategoricalInner<false>(uint32_t,uint32_t,uint32_t,const
  uint32_t *,int,const LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t *) c
  onst' being compiled (compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  c:\users\ntitov\downloads\lightgbm\src\io\sparse_bin.hpp(404): note: while compiling class template member function '
  LightGBM::data_size_t LightGBM::SparseBin<uint32_t>::SplitCategorical(uint32_t,uint32_t,const uint32_t *,int,const Li
  ghtGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t *) const' (compiling source
   file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp(629): note: see reference to class template instantiation 'LightGBM
  ::SparseBin<uint32_t>' being compiled
c:\users\ntitov\downloads\lightgbm\src\io\dense_bin.hpp(310): warning C4100: 'max_bin': unreferenced formal parameter (
compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp) [C:\Users\ntitov\Downloads\LightGBM\build\ligh
tgbm.vcxproj]
  c:\users\ntitov\downloads\lightgbm\src\io\dense_bin.hpp(362): note: see reference to function template instantiation
  'LightGBM::data_size_t LightGBM::DenseBin<uint32_t,false>::SplitCategoricalInner<false>(uint32_t,uint32_t,uint32_t,co
  nst uint32_t *,int,const LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t
  *) const' being compiled (compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  c:\users\ntitov\downloads\lightgbm\src\io\dense_bin.hpp(360): note: see reference to function template instantiation
  'LightGBM::data_size_t LightGBM::DenseBin<uint32_t,false>::SplitCategoricalInner<false>(uint32_t,uint32_t,uint32_t,co
  nst uint32_t *,int,const LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t
  *) const' being compiled (compiling source file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  c:\users\ntitov\downloads\lightgbm\src\io\dense_bin.hpp(359): note: while compiling class template member function 'L
  ightGBM::data_size_t LightGBM::DenseBin<uint32_t,false>::SplitCategorical(uint32_t,uint32_t,const uint32_t *,int,cons
  t LightGBM::data_size_t *,LightGBM::data_size_t,LightGBM::data_size_t *,LightGBM::data_size_t *) const' (compiling so
  urce file C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp)
  C:\Users\ntitov\Downloads\LightGBM\src\io\bin.cpp(625): note: see reference to class template instantiation 'LightGBM
  ::DenseBin<uint32_t,false>' being compiled
  json11.cpp
  metadata.cpp
  parser.cpp
  tree.cpp
  dcg_calculator.cpp
  metric.cpp
  linker_topo.cpp
  linkers_mpi.cpp
  linkers_socket.cpp
  network.cpp
  objective_function.cpp
  data_parallel_tree_learner.cpp
  feature_parallel_tree_learner.cpp
  gpu_tree_learner.cpp
  serial_tree_learner.cpp
  tree_learner.cpp
  voting_parallel_tree_learner.cpp
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(203): warning C4800: 'signed char': f
orcing value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\lightgbm.vcxproj
]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(176): note: while compiling class t
  emplate member function 'void LightGBM::DataParallelTreeLearner<LightGBM::GPUTreeLearner>::FindBestSplitsFromHistogra
  ms(const std::vector<int8_t,std::allocator<_Ty>> &,bool,const LightGBM::Tree *)'
          with
          [
              _Ty=int8_t
          ]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(171): note: see reference to functi
  on template instantiation 'void LightGBM::DataParallelTreeLearner<LightGBM::GPUTreeLearner>::FindBestSplitsFromHistog
  rams(const std::vector<int8_t,std::allocator<_Ty>> &,bool,const LightGBM::Tree *)' being compiled
          with
          [
              _Ty=int8_t
          ]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(259): note: see reference to class
  template instantiation 'LightGBM::DataParallelTreeLearner<LightGBM::GPUTreeLearner>' being compiled
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\data_parallel_tree_learner.cpp(217): warning C4800: 'signed char': f
orcing value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\lightgbm.vcxproj
]
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\serial_tree_learner.cpp(388): warning C4800: 'signed char': forcing
value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\lightgbm.vcxproj]
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\serial_tree_learner.cpp(410): warning C4800: 'signed char': forcing
value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\lightgbm.vcxproj]
c:\users\ntitov\downloads\lightgbm\src\objective\objective_function.cpp(52): warning C4702: unreachable code [C:\Users\
ntitov\Downloads\LightGBM\build\lightgbm.vcxproj]
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(378): warning C4800: 'signed char':
 forcing value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\lightgbm.vcxpr
oj]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(350): note: while compiling class
   template member function 'void LightGBM::VotingParallelTreeLearner<LightGBM::GPUTreeLearner>::FindBestSplitsFromHist
  ograms(const std::vector<int8_t,std::allocator<_Ty>> &,bool,const LightGBM::Tree *)'
          with
          [
              _Ty=int8_t
          ]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(346): note: see reference to func
  tion template instantiation 'void LightGBM::VotingParallelTreeLearner<LightGBM::GPUTreeLearner>::FindBestSplitsFromHi
  stograms(const std::vector<int8_t,std::allocator<_Ty>> &,bool,const LightGBM::Tree *)' being compiled
          with
          [
              _Ty=int8_t
          ]
  C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(457): note: see reference to clas
  s template instantiation 'LightGBM::VotingParallelTreeLearner<LightGBM::GPUTreeLearner>' being compiled
C:\Users\ntitov\Downloads\LightGBM\src\treelearner\voting_parallel_tree_learner.cpp(394): warning C4800: 'signed char':
 forcing value to bool 'true' or 'false' (performance warning) [C:\Users\ntitov\Downloads\LightGBM\build\lightgbm.vcxpr
oj]
c:\users\ntitov\downloads\lightgbm\src\treelearner\serial_tree_learner.cpp(233): warning C4702: unreachable code [C:\Us
ers\ntitov\Downloads\LightGBM\build\lightgbm.vcxproj]
     Creating library C:/Users/ntitov/Downloads/LightGBM/Release/lightgbm.lib and object C:/Users/ntitov/Downloads/Ligh
  tGBM/Release/lightgbm.exp
  lightgbm.vcxproj -> C:\Users\ntitov\Downloads\LightGBM\Release\lightgbm.exe
  Building Custom Rule C:/Users/ntitov/Downloads/LightGBM/CMakeLists.txt

To reproduce run code from the guide:

git clone --recursive https://github.com/microsoft/LightGBM
cd LightGBM
mkdir build
cd build
cmake -A x64 ..
cmake --build . --target ALL_BUILD --config Release

[guolinke]

I think these warnings are generated by template function variable, and cannot be fixed.
And compiler should not throw these warnings.

[guolinke]

for example, it throws max_bin is not used in the following function.

LightGBM/src/io/dense_bin.hpp

Lines 309 to 342 in dc963d9

	template <bool USE_MIN_BIN>
	data_size_t SplitCategoricalInner(uint32_t min_bin, uint32_t max_bin,
	uint32_t most_freq_bin,
	const uint32_t* threshold,
	int num_threshold,
	const data_size_t* data_indices,
	data_size_t cnt, data_size_t* lte_indices,
	data_size_t* gt_indices) const {
	data_size_t lte_count = 0;
	data_size_t gt_count = 0;
	data_size_t* default_indices = gt_indices;
	data_size_t* default_count = &gt_count;
	int8_t offset = most_freq_bin == 0 ? 1 : 0;
	if (most_freq_bin > 0 &&
	Common::FindInBitset(threshold, num_threshold, most_freq_bin)) {
	default_indices = lte_indices;
	default_count = &lte_count;
	}
	for (data_size_t i = 0; i < cnt; ++i) {
	const data_size_t idx = data_indices[i];
	const uint32_t bin = data(idx);
	if (USE_MIN_BIN && (bin < min_bin || bin > max_bin)) {
	default_indices[(*default_count)++] = idx;
	} else if (!USE_MIN_BIN && bin == 0) {
	default_indices[(*default_count)++] = idx;
	} else if (Common::FindInBitset(threshold, num_threshold,
	bin - min_bin + offset)) {
	lte_indices[lte_count++] = idx;
	} else {
	gt_indices[gt_count++] = idx;
	}
	}
	return lte_count;
	}

But when USE_MIN_BIN is true, max_bin is used.

[StrikerRUS]

@guolinke Yeah, possibly. But some of them can be fixed and are not related to templates I believe. For instance,

c:\users\ntitov\downloads\lightgbm\src\boosting\prediction_early_stop.cpp(88): warning C4702: unreachable code [C:\User
s\ntitov\Downloads\LightGBM\build\_lightgbm.vcxproj]

[StrikerRUS]

Also, we have the following warnings with gcc for GPU version:

[ 83%] Building CXX object CMakeFiles/_lightgbm.dir/src/treelearner/gpu_tree_learner.cpp.o
In file included from /usr/include/boost/property_tree/json_parser/detail/parser.hpp:7:0,
                 from /usr/include/boost/property_tree/json_parser/detail/read.hpp:13,
                 from /usr/include/boost/property_tree/json_parser.hpp:16,
                 from /__w/1/s/compute/include/boost/compute/detail/parameter_cache.hpp:31,
                 from /__w/1/s/compute/include/boost/compute/algorithm/detail/copy_on_device.hpp:23,
                 from /__w/1/s/compute/include/boost/compute/algorithm/copy.hpp:26,
                 from /__w/1/s/compute/include/boost/compute/container/vector.hpp:32,
                 from /__w/1/s/src/treelearner/gpu_tree_learner.h:34,
                 from /__w/1/s/src/treelearner/parallel_tree_learner.h:15,
                 from /__w/1/s/src/treelearner/data_parallel_tree_learner.cpp:9:
/usr/include/boost/bind.hpp:41:265: note: #pragma message: The practice of declaring the Bind placeholders (_1, _2, ...) in the global namespace is deprecated. Please use <boost/bind/bind.hpp> + using namespace boost::placeholders, or define BOOST_BIND_GLOBAL_PLACEHOLDERS to retain the current behavior.
 )

<repeated a lot>

https://dev.azure.com/lightgbm-ci/lightgbm-ci/_build/results?buildId=7330&view=logs&j=9ce42e5d-f31a-544a-a6de-dc42f8c013ed&t=b696def5-78ae-590c-4234-04332342ba2d

But it looks like a problem in boost codebase itself, not with our GPU learner code, right? @huanzhang12

[guolinke]

@StrikerRUS
yeah, for that warning, it is introduced by code refactoring.

for the rest type conversion errors, we can fix them.

[StrikerRUS]

@guolinke

yeah, for that warning, it is introduced by code refactoring.

I remember that refactoring was done to workaround warning from VS 2019 about that not all code paths return value. I think we should prefer eliminating warnings from the most recent VS versions.

[github-actions]

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