C++ Mathematical Expression Library (ExprTk)  http://www.partow.net/programming/exprtk/index.html
diff --git a/Makefile b/Makefile
index 95939c6..16e0357 100644
--- a/Makefile
+++ b/Makefile
@@ -21,10 +21,11 @@
 BASE_OPTIONS     := -pedantic-errors -Wall -Wextra -Werror -Wno-long-long
 OPTIONS          := $(BASE_OPTIONS) $(OPTIMIZATION_OPT)
 LINKER_OPT       := -L/usr/lib -lstdc++ -lm
-ASAN_OPT         := -g -fsanitize=address -fno-omit-frame-pointer
-MSAN_OPT         := -g -fsanitize=memory  -fno-omit-frame-pointer
-LSAN_OPT         := -g -fsanitize=leak    -fno-omit-frame-pointer
-BUILD_SRC        := $(wildcard exprtk_*.cpp)
+ASAN_OPT         := -g -fsanitize=address   -fno-omit-frame-pointer
+MSAN_OPT         := -g -fsanitize=memory    -fno-omit-frame-pointer
+LSAN_OPT         := -g -fsanitize=leak      -fno-omit-frame-pointer
+USAN_OPT         := -g -fsanitize=undefined -fno-omit-frame-pointer
+BUILD_SRC        := $(sort $(wildcard exprtk_*.cpp))
 BUILD_LIST       := $(BUILD_SRC:%.cpp=%)
 
 
diff --git a/exprtk.hpp b/exprtk.hpp
index aafb846..6043aa6 100644
--- a/exprtk.hpp
+++ b/exprtk.hpp
@@ -67,7 +67,7 @@
    #define exprtk_error_location             \
    "exprtk.hpp:" + details::to_str(__LINE__) \
 
-   #if __GNUC__  >= 7
+   #if defined(__GNUC__) && (__GNUC__  >= 7)
 
       #define exprtk_disable_fallthrough_begin                      \
       _Pragma ("GCC diagnostic push")                               \
@@ -1320,8 +1320,8 @@
             template <typename T> inline T  frac_impl(const T v, real_type_tag) { return (v - static_cast<long long>(v)); }
             template <typename T> inline T trunc_impl(const T v, real_type_tag) { return T(static_cast<long long>(v));    }
 
-            template <typename T> inline T const_pi_impl(real_type_tag) { return numeric::constant::pi; }
-            template <typename T> inline T const_e_impl (real_type_tag) { return numeric::constant::e;  }
+            template <typename T> inline T const_pi_impl(real_type_tag) { return T(numeric::constant::pi); }
+            template <typename T> inline T const_e_impl (real_type_tag) { return T(numeric::constant::e);  }
 
             template <typename T> inline T   abs_impl(const T v, int_type_tag) { return ((v >= T(0)) ? v : -v); }
             template <typename T> inline T   exp_impl(const T v, int_type_tag) { return std::exp  (v); }
@@ -2780,7 +2780,7 @@
                         Note: The following 'awkward' conditional is
                               due to various broken msvc compilers.
                      */
-                     #if _MSC_VER == 1600
+                     #if defined(_MSC_VER) && (_MSC_VER == 1600)
                      const bool within_range = !is_end(s_itr_ + 2) &&
                                                !is_end(s_itr_ + 3) ;
                      #else
@@ -3761,7 +3761,7 @@
                         case lexer::token::e_sub     : return false;
                         case lexer::token::e_colon   : return false;
                         case lexer::token::e_ternary : return false;
-                        default                      : return true;
+                        default                      : return true ;
                      }
                   }
                }
@@ -3775,7 +3775,7 @@
                      case lexer::token::e_eof     : return false;
                      case lexer::token::e_colon   : return false;
                      case lexer::token::e_ternary : return false;
-                     default                      : return true;
+                     default                      : return true ;
                   }
                }
                else if (details::is_left_bracket(static_cast<char>(t)))
@@ -5963,10 +5963,8 @@
                                 else
                                    return ((T(2) * arg1  <= (arg2 + arg0)) ? arg0 : arg2);
 
-               default        : {
-                                   exprtk_debug(("trinary_node::value() - Error: Invalid operation\n"));
-                                   return std::numeric_limits<T>::quiet_NaN();
-                                }
+               default        : exprtk_debug(("trinary_node::value() - Error: Invalid operation\n"));
+                                return std::numeric_limits<T>::quiet_NaN();
             }
          }
 
diff --git a/exprtk_simple_example_10.cpp b/exprtk_simple_example_10.cpp
index 1f5b910..6ce237b 100644
--- a/exprtk_simple_example_10.cpp
+++ b/exprtk_simple_example_10.cpp
@@ -45,22 +45,23 @@
       .add(
       function_t( // define function: newton_sqrt(x)
            "newton_sqrt",
-           " switch                                              "
-           " {                                                   "
-           "   case x < 0  : -inf;                               "
-           "   case x == 0 : 0;                                  "
-           "   case x == 1 : 1;                                  "
-           "   default:                                          "
-           "   ~{                                                "
-           "      var z := 100;                                  "
-           "      var sqrt_x := x / 2;                           "
-           "      repeat                                         "
-           "        sqrt_x := (1 / 2) * (sqrt_x + (x / sqrt_x)); "
-           "        if (equal(sqrt_x^2, x))                      "
-           "          break[sqrt_x];                             "
-           "      until ((z -= 1) <= 0);                         "
-           "    };                                               "
-           " }                                                   ",
+           " switch                                                "
+           " {                                                     "
+           "   case x < 0  : null;                                 "
+           "   case x == 0 : 0;                                    "
+           "   case x == 1 : 1;                                    "
+           "   default:                                            "
+           "   ~{                                                  "
+           "      var z := 100;                                    "
+           "      var sqrt_x := x / 2;                             "
+           "      repeat                                           "
+           "        if (equal(sqrt_x^2, x))                        "
+           "          break[sqrt_x];                               "
+           "        else                                           "
+           "          sqrt_x := (1 / 2) * (sqrt_x + (x / sqrt_x)); "
+           "      until ((z -= 1) <= 0);                           "
+           "    };                                                 "
+           " }                                                     ",
            "x"));
 
    std::string expression_str = "newton_sqrt(x)";
@@ -77,7 +78,7 @@
 
       T result = expression.value();
 
-      printf("sqrt(%03d) - Result: %12.10f\tReal: %12.10f\n",
+      printf("sqrt(%03d) - Result: %15.13f\tReal: %15.13f\n",
              static_cast<unsigned int>(i),
              result,
              std::sqrt(x));