Fix Visual Studio 2017 new warning (C4244: 'argument': conversion fro… (#4261)

* Fix Visual Studio 2017 new warning (C4244: 'argument': conversion from 'int' to 'const char', possible loss of data)

* Fix Visual Studio 2017 pedantic warnings

* Fix Visual Studio 2017 pedantic warnings

include/flatbuffers/util.h

@@ -114,6 +114,11 @@ inline uint64_t StringToUInt(const char *str, char **endptr = nullptr,
   #endif
 }
 
+// Pedantic warning free version of toupper().
+inline char ToUpper(char c) {
+  return static_cast<char>(::toupper(c));
+}
+
 typedef bool (*LoadFileFunction)(const char *filename, bool binary,
                                  std::string *dest);
 typedef bool (*FileExistsFunction)(const char *filename);

src/idl_gen_cpp.cpp

@@ -54,7 +54,7 @@ class CppGenerator : public BaseGenerator {
       guard += *it + "_";
     }
     guard += "H_";
-    std::transform(guard.begin(), guard.end(), guard.begin(), ::toupper);
+    std::transform(guard.begin(), guard.end(), guard.begin(), ToUpper);
     return guard;
   }
 
@@ -852,7 +852,7 @@ class CppGenerator : public BaseGenerator {
 
   std::string GenFieldOffsetName(const FieldDef &field) {
     std::string uname = field.name;
-    std::transform(uname.begin(), uname.end(), uname.begin(), ::toupper);
+    std::transform(uname.begin(), uname.end(), uname.begin(), ToUpper);
     return "VT_" + uname;
   }
 

tests/test.cpp

@@ -261,7 +261,7 @@ void AccessFlatBufferTest(const uint8_t *flatbuf, size_t length,
   // Test accessing a vector of sorted structs
   auto vecofstructs = monster->testarrayofsortedstruct();
   if (vecofstructs) {  // not filled in monster_test.bfbs
-    for (size_t i = 0; i < vecofstructs->size()-1; i++) {
+    for (flatbuffers::uoffset_t i = 0; i < vecofstructs->size()-1; i++) {
       auto left = vecofstructs->Get(i);
       auto right = vecofstructs->Get(i+1);
       TEST_EQ(true, (left->KeyCompareLessThan(right)));