Question

I have two constructors overloaded like this, the problem is that the wrong constructor overload is entered :

class Param
{ 
    Param(
     const std::string& name,
     const MyVariant& variant = MyVariant()
     const std::string& desc = std::string(""),
     bool b1 = true,
     bool b2 = true )
     :
     mName(name),
     mValue(variant),
     mDesc(desc),
     mB1(b1),
     mB2(b2) {}

     Param( 
      const std::string& name,
      const MyVariant& variant,
      bool b1)
      :
      mName(name),
      mValue(variant)
      mB1(b1) {}

   private:
      std::string mName;
      MyVariant mValue;
      std::string mDesc;
      bool mB1;
      bool mB2;
};

 Param p("name",4,"desc"); // this enters the second constructor, not the first why ? 

Answer 1

It uses the second constructor because "desc" is a const char* that can be converted to a bool implicitly, so that’s what the compiler does. There is no implicit conversion from const char* to std::string, so the first constructor is not even a candidate here.

To use the first constructor you ‘d need to explicitly pass in a string:

Param p("name",4,std::string("desc"));