Improve runtime error handling

src/execute/error.cpp

@@ -2,5 +2,43 @@
 
 namespace Execute
 {
-	
+	std::string const & RuntimeError::GetMessage() const
+	{
+		return message;
+	}
+
+	RuntimeError::RuntimeError()
+		: message("Undocumented runtime error")
+	{
+	}
+
+	RuntimeError::RuntimeError(std::string const & what)
+		: message(what)
+	{
+	}
+
+	StackUnderflow::StackUnderflow()
+		: RuntimeError("Stack underflow error")
+	{
+	}
+
+	StackOverflow::StackOverflow()
+		: RuntimeError("Stack overflow error")
+	{
+	}
+
+	MissingLabel::MissingLabel(std::string const & label)
+	{
+		message = "Missing jump/function label \"";
+		message += label;
+		message += '"';
+	}
+
+	namespace Internal
+	{
+		BadValueType::BadValueType()
+			: RuntimeError("Internal error: bad value type")
+		{
+		}
+	}
 }