Fix: Make CXXOPTS_NO_EXCEPTIONS compilable and print messages (#196)

Fix CXXOPTS_NO_EXCEPTIONS so that it doesn't warn about unused parameters, and print out error messages.

include/cxxopts.hpp

@@ -467,6 +467,26 @@ namespace cxxopts
     }
   };
 
+  template <typename T>
+  void throw_or_mimic(const std::string& text)
+  {
+    static_assert(std::is_base_of<std::exception, T>::value,
+                  "throw_or_mimic only works on std::exception and "
+                  "deriving classes");
+
+#ifndef CXXOPTS_NO_EXCEPTIONS
+    // If CXXOPTS_NO_EXCEPTIONS is not defined, just throw
+    throw T{text};
+#else
+    // Otherwise manually instantiate the exception, print what() to stderr,
+    // and abort
+    T exception{text};
+    std::cerr << exception.what() << std::endl;
+    std::cerr << "Aborting (exceptions disabled)..." << std::endl;
+    std::abort();
+#endif
+  }
+
   namespace values
   {
     namespace
@@ -495,22 +515,14 @@ namespace cxxopts
           {
             if (u > static_cast<U>((std::numeric_limits<T>::min)()))
             {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+              throw_or_mimic<argument_incorrect_type>(text);
-              throw argument_incorrect_type(text);
-#else
-              std::abort();
-#endif
             }
           }
           else
           {
             if (u > static_cast<U>((std::numeric_limits<T>::max)()))
             {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+              throw_or_mimic<argument_incorrect_type>(text);
-              throw argument_incorrect_type(text);
-#else
-              std::abort();
-#endif
             }
           }
         }
@@ -544,13 +556,10 @@ namespace cxxopts
 
     template <typename R, typename T>
     T
-    checked_negate(T&&, const std::string& text, std::false_type)
+    checked_negate(T&& t, const std::string& text, std::false_type)
     {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+      throw_or_mimic<argument_incorrect_type>(text);
-      throw argument_incorrect_type(text);
+      return t;
-#else
-      std::abort();
-#endif
     }
 
     template <typename T>
@@ -562,11 +571,7 @@ namespace cxxopts
 
       if (match.length() == 0)
       {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+        throw_or_mimic<argument_incorrect_type>(text);
-        throw argument_incorrect_type(text);
-#else
-        std::abort();
-#endif
       }
 
       if (match.length(4) > 0)
@@ -603,21 +608,13 @@ namespace cxxopts
         }
         else
         {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+          throw_or_mimic<argument_incorrect_type>(text);
-          throw argument_incorrect_type(text);
-#else
-          std::abort();
-#endif
         }
 
         US next = result * base + digit;
         if (result > next)
         {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+          throw_or_mimic<argument_incorrect_type>(text);
-          throw argument_incorrect_type(text);
-#else
-          std::abort();
-#endif
         }
 
         result = next;
@@ -643,11 +640,7 @@ namespace cxxopts
       std::stringstream in(text);
       in >> value;
       if (!in) {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+        throw_or_mimic<argument_incorrect_type>(text);
-        throw argument_incorrect_type(text);
-#else
-        std::abort();
-#endif
       }
     }
 
@@ -727,11 +720,7 @@ namespace cxxopts
         return;
       }
 
-#ifndef CXXOPTS_NO_EXCEPTIONS
+      throw_or_mimic<argument_incorrect_type>(text);
-      throw argument_incorrect_type(text);
-#else
-      std::abort();
-#endif
     }
 
     inline
@@ -1108,11 +1097,7 @@ namespace cxxopts
     as() const
     {
       if (m_value == nullptr) {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+        throw_or_mimic<std::domain_error>("No value");
-        throw std::domain_error("No value");
-#else
-        std::abort();
-#endif
       }
 
 #ifdef CXXOPTS_NO_RTTI
@@ -1207,11 +1192,7 @@ namespace cxxopts
 
       if (iter == m_options->end())
       {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+        throw_or_mimic<option_not_present_exception>(option);
-        throw option_not_present_exception(option);
-#else
-        std::abort();
-#endif
       }
 
       auto riter = m_results.find(iter->second);
@@ -1633,11 +1614,7 @@ OptionAdder::operator()
 
   if (result.empty())
   {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+    throw_or_mimic<invalid_option_format_error>(opts);
-    throw invalid_option_format_error(opts);
-#else
-    std::abort();
-#endif
   }
 
   const auto& short_match = result[2];
@@ -1645,18 +1622,10 @@ OptionAdder::operator()
 
   if (!short_match.length() && !long_match.length())
   {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+    throw_or_mimic<invalid_option_format_error>(opts);
-    throw invalid_option_format_error(opts);
-#else
-    std::abort();
-#endif
   } else if (long_match.length() == 1 && short_match.length())
   {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+    throw_or_mimic<invalid_option_format_error>(opts);
-    throw invalid_option_format_error(opts);
-#else
-    std::abort();
-#endif
   }
 
   auto option_names = []
@@ -1729,11 +1698,7 @@ ParseResult::checked_parse_arg
     }
     else
     {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+      throw_or_mimic<missing_argument_exception>(name);
-      throw missing_argument_exception(name);
-#else
-      std::abort();
-#endif
     }
   }
   else
@@ -1758,11 +1723,7 @@ ParseResult::add_to_option(const std::string& option, const std::string& arg)
 
   if (iter == m_options->end())
   {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+    throw_or_mimic<option_not_exists_exception>(option);
-    throw option_not_exists_exception(option);
-#else
-    std::abort();
-#endif
   }
 
   parse_option(iter->second, option, arg);
@@ -1800,11 +1761,7 @@ ParseResult::consume_positional(std::string a)
     }
     else
     {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+      throw_or_mimic<option_not_exists_exception>(*m_next_positional);
-      throw option_not_exists_exception(*m_next_positional);
-#else
-      std::abort();
-#endif
     }
   }
 
@@ -1872,11 +1829,7 @@ ParseResult::parse(int& argc, char**& argv)
       // but if it starts with a `-`, then it's an error
       if (argv[current][0] == '-' && argv[current][1] != '\0') {
         if (!m_allow_unrecognised) {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+          throw_or_mimic<option_syntax_exception>(argv[current]);
-          throw option_syntax_exception(argv[current]);
-#else
-          std::abort();
-#endif
         }
       }
 
@@ -1913,11 +1866,7 @@ ParseResult::parse(int& argc, char**& argv)
             else
             {
               //error
-#ifndef CXXOPTS_NO_EXCEPTIONS
+              throw_or_mimic<option_not_exists_exception>(name);
-              throw option_not_exists_exception(name);
-#else
-              std::abort();
-#endif
             }
           }
 
@@ -1935,11 +1884,7 @@ ParseResult::parse(int& argc, char**& argv)
           else
           {
             //error
-#ifndef CXXOPTS_NO_EXCEPTIONS
+            throw_or_mimic<option_requires_argument_exception>(name);
-            throw option_requires_argument_exception(name);
-#else
-            std::abort();
-#endif
           }
         }
       }
@@ -1962,11 +1907,7 @@ ParseResult::parse(int& argc, char**& argv)
           else
           {
             //error
-#ifndef CXXOPTS_NO_EXCEPTIONS
+            throw_or_mimic<option_not_exists_exception>(name);
-            throw option_not_exists_exception(name);
-#else
-            std::abort();
-#endif
           }
         }
 
@@ -2084,11 +2025,7 @@ Options::add_one_option
 
   if (!in.second)
   {
-#ifndef CXXOPTS_NO_EXCEPTIONS
+    throw_or_mimic<option_exists_error>(option);
-    throw option_exists_error(option);
-#else
-    std::abort();
-#endif
   }
 }