changed sprintf uses to snprintf (#2920)

* [ci] changed sprintf uses to snprintf

* checked for encoding issues with snprintf

include/LightGBM/utils/common.h

@@ -376,16 +376,13 @@ inline static void Int32ToStr(int32_t value, char* buffer) {
   Uint32ToStr(u, buffer);
 }
 
-inline static void DoubleToStr(double value, char* buffer, size_t
+inline static void DoubleToStr(double value, char* buffer, size_t buffer_len) {
   #ifdef _MSC_VER
-                               buffer_len
-                               #endif
-) {
-  #ifdef _MSC_VER
-  sprintf_s(buffer, buffer_len, "%.17g", value);
+  int num_chars = sprintf_s(buffer, buffer_len, "%.17g", value);
   #else
-  sprintf(buffer, "%.17g", value);
+  int num_chars = snprintf(buffer, buffer_len, "%.17g", value);
   #endif
+  CHECK_GE(num_chars, 0);
 }
 
 inline static const char* SkipSpaceAndTab(const char* p) {
@@ -420,17 +417,14 @@ struct __TToStringHelperFast {
 
 template<typename T>
 struct __TToStringHelperFast<T, true, false> {
-  void operator()(T value, char* buffer, size_t
-                  #ifdef _MSC_VER
-                  buf_len
-                  #endif
-                  )
+  void operator()(T value, char* buffer, size_t buf_len)
   const {
     #ifdef _MSC_VER
-    sprintf_s(buffer, buf_len, "%g", value);
+    int num_chars = sprintf_s(buffer, buf_len, "%g", value);
     #else
-    sprintf(buffer, "%g", value);
+    int num_chars = snprintf(buffer, buf_len, "%g", value);
     #endif
+    CHECK_GE(num_chars, 0);
   }
 };