simple exception handle and error message. Need RAII in the future.

include/LightGBM/c_api.h

 #ifndef LIGHTGBM_C_API_H_
 #define LIGHTGBM_C_API_H_
-#include<cstdint>
-
-
+#include <cstdint>
+#include <exception>
+#include <stdexcept>
+#include <string>
 /*!
 * To avoid type conversion on large data, most of our expose interface support both for float_32 and float_64.
 * Except following:
@@ -412,4 +413,30 @@ ColumnFunctionFromCSC(const void* col_ptr, int col_ptr_type, const int32_t* indi
 std::vector<double> 
 SampleFromOneColumn(const std::vector<std::pair<int, double>>& data, const std::vector<size_t>& indices);
 
+
+// exception handle and error msg
+
+static std::string& LastErrorMsg() { static std::string err_msg("Everything is fine"); return err_msg; }
+
+inline void LGBM_SetLastError(const char* msg) {
+  LastErrorMsg() = msg;
+}
+
+inline int LGBM_APIHandleException(const std::exception& ex) {
+  LGBM_SetLastError(ex.what());
+  return -1;
+}
+inline int LGBM_APIHandleException(const std::string& ex) {
+  LGBM_SetLastError(ex.c_str());
+  return -1;
+}
+
+#define API_BEGIN() try {
+
+#define API_END() } \
+catch(std::exception& ex) { return LGBM_APIHandleException(ex); } \
+catch(std::string& ex) { return LGBM_APIHandleException(ex); } \
+catch(...) { return LGBM_APIHandleException("unknown exception"); } \
+return 0;  
+
 #endif // LIGHTGBM_C_API_H_

include/LightGBM/utils/log.h

@@ -5,6 +5,8 @@
 #include <cstdlib>
 #include <cstdarg>
 #include <cstring>
+#include <exception>
+#include <stdexcept>
 
 namespace LightGBM {
 
@@ -62,13 +64,15 @@ public:
   }
   static void Fatal(const char *format, ...) {
     va_list val;
+    char str_buf[1024];
     va_start(val, format);
-    fprintf(stderr, "[LightGBM] [Fatal] ");
-    vfprintf(stderr, format, val);
-    fprintf(stderr, "\n");
-    fflush(stderr);
+#ifdef _MSC_VER
+    vsprintf_s(str_buf, format, val);
+#else
+    vsprintf(str_buf, format, val);
+#endif
     va_end(val);
-    exit(1);
+    throw std::runtime_error(std::string(str_buf));
   }
 
 private:

src/c_api.cpp

@@ -158,18 +158,15 @@ private:
 
 using namespace LightGBM;
 
-
 DllExport const char* LGBM_GetLastError() {
-  return "Not error msg now, will support soon";
+  return LastErrorMsg().c_str();
 }
 
-
-
 DllExport int LGBM_CreateDatasetFromFile(const char* filename,
   const char* parameters,
   const DatesetHandle* reference,
   DatesetHandle* out) {
-
+  API_BEGIN();
   OverallConfig config;
   config.LoadFromString(parameters);
   DatasetLoader loader(config.io_config, nullptr);
@@ -179,17 +176,16 @@ DllExport int LGBM_CreateDatasetFromFile(const char* filename,
   } else {
     *out = loader.LoadFromFileAlignWithOtherDataset(filename, reinterpret_cast<const Dataset*>(*reference));
   }
-  return 0;
+  API_END();
 }
 
-
 DllExport int LGBM_CreateDatasetFromBinaryFile(const char* filename,
   DatesetHandle* out) {
-
+  API_BEGIN();
   OverallConfig config;
   DatasetLoader loader(config.io_config, nullptr);
   *out = loader.LoadFromBinFile(filename, 0, 1);
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_CreateDatasetFromMat(const void* data,
@@ -200,7 +196,7 @@ DllExport int LGBM_CreateDatasetFromMat(const void* data,
   const char* parameters,
   const DatesetHandle* reference,
   DatesetHandle* out) {
-
+  API_BEGIN();
   OverallConfig config;
   config.LoadFromString(parameters);
   DatasetLoader loader(config.io_config, nullptr);
@@ -235,7 +231,7 @@ DllExport int LGBM_CreateDatasetFromMat(const void* data,
   }
   ret->FinishLoad();
   *out = ret;
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_CreateDatasetFromCSR(const void* indptr,
@@ -249,7 +245,7 @@ DllExport int LGBM_CreateDatasetFromCSR(const void* indptr,
   const char* parameters,
   const DatesetHandle* reference,
   DatesetHandle* out) {
-
+  API_BEGIN();
   OverallConfig config;
   config.LoadFromString(parameters);
   DatasetLoader loader(config.io_config, nullptr);
@@ -295,10 +291,9 @@ DllExport int LGBM_CreateDatasetFromCSR(const void* indptr,
   ret->FinishLoad();
   *out = ret;
 
-  return 0;
+  API_END();
 }
 
-
 DllExport int LGBM_CreateDatasetFromCSC(const void* col_ptr,
   int col_ptr_type,
   const int32_t* indices,
@@ -310,6 +305,7 @@ DllExport int LGBM_CreateDatasetFromCSC(const void* col_ptr,
   const char* parameters,
   const DatesetHandle* reference,
   DatesetHandle* out) {
+  API_BEGIN();
   OverallConfig config;
   config.LoadFromString(parameters);
   DatasetLoader loader(config.io_config, nullptr);
@@ -342,20 +338,22 @@ DllExport int LGBM_CreateDatasetFromCSC(const void* col_ptr,
   }
   ret->FinishLoad();
   *out = ret;
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_DatasetFree(DatesetHandle handle) {
+  API_BEGIN();
   auto dataset = reinterpret_cast<Dataset*>(handle);
   delete dataset;
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_DatasetSaveBinary(DatesetHandle handle,
   const char* filename) {
+  API_BEGIN();
   auto dataset = reinterpret_cast<Dataset*>(handle);
   dataset->SaveBinaryFile(filename);
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_DatasetSetField(DatesetHandle handle,
@@ -363,6 +361,7 @@ DllExport int LGBM_DatasetSetField(DatesetHandle handle,
   const void* field_data,
   int64_t num_element,
   int type) {
+  API_BEGIN();
   auto dataset = reinterpret_cast<Dataset*>(handle);
   bool is_success = false;
   if (type == C_API_DTYPE_FLOAT32) {
@@ -370,8 +369,8 @@ DllExport int LGBM_DatasetSetField(DatesetHandle handle,
   } else if (type == C_API_DTYPE_INT32) {
     is_success = dataset->SetIntField(field_name, reinterpret_cast<const int*>(field_data), static_cast<int32_t>(num_element));
   }
-  if (is_success) { return 0; }
-  return -1;
+  if (!is_success) { throw std::runtime_error("Input data type erorr or field not found"); }
+  API_END();
 }
 
 DllExport int LGBM_DatasetGetField(DatesetHandle handle,
@@ -379,29 +378,34 @@ DllExport int LGBM_DatasetGetField(DatesetHandle handle,
   int64_t* out_len,
   const void** out_ptr,
   int* out_type) {
+  API_BEGIN();
   auto dataset = reinterpret_cast<Dataset*>(handle);
+  bool is_success = false;
   if (dataset->GetFloatField(field_name, out_len, reinterpret_cast<const float**>(out_ptr))) {
     *out_type = C_API_DTYPE_FLOAT32;
-    return 0;
+    is_success = true;
   } else if (dataset->GetIntField(field_name, out_len, reinterpret_cast<const int**>(out_ptr))) {
     *out_type = C_API_DTYPE_INT32;
-    return 0;
+    is_success = true;
   }
-  return -1;
+  if (!is_success) { throw std::runtime_error("Field not found"); }
+  API_END();
 }
 
 DllExport int LGBM_DatasetGetNumData(DatesetHandle handle,
   int64_t* out) {
+  API_BEGIN();
   auto dataset = reinterpret_cast<Dataset*>(handle);
   *out = dataset->num_data();
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_DatasetGetNumFeature(DatesetHandle handle,
   int64_t* out) {
+  API_BEGIN();
   auto dataset = reinterpret_cast<Dataset*>(handle);
   *out = dataset->num_total_features();
-  return 0;
+  API_END();
 }
 
 
@@ -413,6 +417,7 @@ DllExport int LGBM_BoosterCreate(const DatesetHandle train_data,
   int n_valid_datas,
   const char* parameters,
   BoosterHandle* out) {
+  API_BEGIN();
   const Dataset* p_train_data = reinterpret_cast<const Dataset*>(train_data);
   std::vector<const Dataset*> p_valid_datas;
   std::vector<std::string> p_valid_names;
@@ -421,51 +426,54 @@ DllExport int LGBM_BoosterCreate(const DatesetHandle train_data,
     p_valid_names.emplace_back(valid_names[i]);
   }
   *out = new Booster(p_train_data, p_valid_datas, p_valid_names, parameters);
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterLoadFromModelfile(
   const char* filename,
   BoosterHandle* out) {
+  API_BEGIN();
   *out = new Booster(filename);
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterFree(BoosterHandle handle) {
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   delete ref_booster;
-  return 0;
+  API_END();
 }
 
-
 DllExport int LGBM_BoosterUpdateOneIter(BoosterHandle handle, int* is_finished) {
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   if (ref_booster->TrainOneIter()) {
     *is_finished = 1;
   } else {
     *is_finished = 0;
   }
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterUpdateOneIterCustom(BoosterHandle handle,
   const float* grad,
   const float* hess,
   int* is_finished) {
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   if (ref_booster->TrainOneIter(grad, hess)) {
     *is_finished = 1;
   } else {
     *is_finished = 0;
   }
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterEval(BoosterHandle handle,
   int data,
   int64_t* out_len,
   float* out_results) {
-
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   auto boosting = ref_booster->GetBoosting();
   auto result_buf = boosting->GetEvalAt(data);
@@ -473,32 +481,31 @@ DllExport int LGBM_BoosterEval(BoosterHandle handle,
   for (size_t i = 0; i < result_buf.size(); ++i) {
     (out_results)[i] = static_cast<float>(result_buf[i]);
   }
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterGetScore(BoosterHandle handle,
   int64_t* out_len,
   const float** out_result) {
-
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   int len = 0;
   *out_result = ref_booster->GetTrainingScore(&len);
   *out_len = static_cast<int64_t>(len);
-
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterGetPredict(BoosterHandle handle,
   int data,
   int64_t* out_len,
   float* out_result) {
-
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   auto boosting = ref_booster->GetBoosting();
   int len = 0;
   boosting->GetPredictAt(data, out_result, &len);
   *out_len = static_cast<int64_t>(len);
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterPredictForFile(BoosterHandle handle,
@@ -507,12 +514,12 @@ DllExport int LGBM_BoosterPredictForFile(BoosterHandle handle,
   int data_has_header,
   const char* data_filename,
   const char* result_filename) {
-
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   ref_booster->PrepareForPrediction(static_cast<int>(n_used_trees), predict_type);
   bool bool_data_has_header = data_has_header > 0 ? true : false;
   ref_booster->PredictForFile(data_filename, result_filename, bool_data_has_header);
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterPredictForCSR(BoosterHandle handle,
@@ -527,7 +534,7 @@ DllExport int LGBM_BoosterPredictForCSR(BoosterHandle handle,
   int predict_type,
   int64_t n_used_trees,
   double* out_result) {
-
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   ref_booster->PrepareForPrediction(static_cast<int>(n_used_trees), predict_type);
 
@@ -542,7 +549,7 @@ DllExport int LGBM_BoosterPredictForCSR(BoosterHandle handle,
       out_result[i * num_class + j] = predicton_result[j];
     }
   }
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterPredictForMat(BoosterHandle handle,
@@ -554,7 +561,7 @@ DllExport int LGBM_BoosterPredictForMat(BoosterHandle handle,
   int predict_type,
   int64_t n_used_trees,
   double* out_result) {
-
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   ref_booster->PrepareForPrediction(static_cast<int>(n_used_trees), predict_type);
 
@@ -568,16 +575,16 @@ DllExport int LGBM_BoosterPredictForMat(BoosterHandle handle,
       out_result[i * num_class + j] = predicton_result[j];
     }
   }
-  return 0;
+  API_END();
 }
 
 DllExport int LGBM_BoosterSaveModel(BoosterHandle handle,
   int num_used_model,
   const char* filename) {
-
+  API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
   ref_booster->SaveModelToFile(num_used_model, filename);
-  return 0;
+  API_END();
 }
 
 // ---- start of some help functions

src/main.cpp

+#include <iostream>
 #include <LightGBM/application.h>
 
 int main(int argc, char** argv) {
+  try {
     LightGBM::Application app(argc, argv);
     app.Run();
+  }
+  catch (const std::exception& ex) {
+    std::cerr << "Met Exceptions:" << std::endl;
+    std::cerr << ex.what() << std::endl;
+    exit(-1);
+  }
+  catch (const std::string& ex) {
+    std::cerr << "Met Exceptions:" << std::endl;
+    std::cerr << ex << std::endl;
+    exit(-1);
+  }
+  catch (...) {
+    std::cerr << "Unknown Exceptions" << std::endl;
+    exit(-1);
+  }
 }