Add more CTL content

ctl/runtime_error.h

@@ -0,0 +1,33 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_RUNTIME_ERROR_H_
+#define CTL_RUNTIME_ERROR_H_
+#include "ctl/string.h"
+
+namespace ctl {
+
+class runtime_error
+{
+  public:
+    explicit runtime_error(const string& what_arg) : msg_(what_arg)
+    {
+    }
+
+    explicit runtime_error(const char* what_arg) : msg_(what_arg)
+    {
+    }
+
+    virtual ~runtime_error() noexcept = default;
+
+    virtual const char* what() const noexcept
+    {
+        return msg_.c_str();
+    }
+
+  private:
+    string msg_;
+};
+
+} // namespace ctl
+
+#endif // CTL_RUNTIME_ERROR_H_