Try fix

include/sparrow/utils/large_int.hpp

@@ -101,7 +101,7 @@ namespace sparrow
         }
         while (n > 0)
         {
-            str += '0' + static_cast<char>(n % 10);
+            str.push_back(static_cast<char>('0' + std::int8_t(n % 10)));
             n /= 10;
         }