CODEWITHSUNDEEP
c++
D Anon
D Anon

Reputation: 11

c++ g++ compiler - error: definition of implicitly-declared

I have searched textbooks and the web. I can't seem to find anything to explain the errors at the bottom. They are coming from the Copy constuctor and the operator= overload.

  1 #ifndef SURVEYDATA_H
  2 #define SURVEYDATA_H
  3
  4 class SurveyData
  5 {
  6     public:
  7         int   getSector();
  8         int   getExposure();
  9         int   getSpeed();
 10
 11         SurveyData();
 12         SurveyData(int, int, int);
 13         SurveyData(const SurveyData&);
 14
 15         SurveyData& operator=(const SurveyData&);
 16     private:
 17         int sector;
 18         int exposure;
 19         int speed;
 20 };
 21 #endif

Header File ^

 SurveyData::SurveyData(const SurveyData& s)
 18 {
 19     sector = s.getSector();
 20     exposure = s.getExposure();
 21     speed = s.getSpeed();
 22 }
 23
 24 SurveyData& SurveyData::operator=(const SurveyData& s)
 25 {
 26     sector = s.getSector();
 27     exposure = s.getExposure();
 28     speed = s.getSpeed();
 29     return *this;
 30 }

Section of .cpp file error is coming from ^

surveydata.cpp:17:43: error: definition of implicitly-declared ‘constexpr SurveyData::SurveyData(const SurveyData&)’
     SurveyData::SurveyData(const SurveyData& s)
                                               ^
    surveydata.cpp:24:54: error: definition of implicitly-declared ‘constexpr SurveyData& SurveyData::operator=(const SurveyData&)’
     SurveyData& SurveyData::operator=(const SurveyData& s)

Errors ^ Any help understanding this is appreciated.

Upvotes: 1

Views: 725

Answers (1)

selbie
selbie

Reputation: 104514

What the H.Krisnan said in the comment. Make those get functions const. That's probably goodness for any place outside of your class where it makes sense to pass a SurveyData by const reference. So go ahead and do that.

However....

You actually don't need a copy constructor nor an overloaded assignment operator in your class. Since your class doesn't have any allocated pointers or members that can't be serviced with a shallow copy, the default copy constructor and default assignment operator generated by the compiler will do nicely. So later when you add a new variable to SurveyData, you won't introduce a bug because you forgot to update the copy constructor.

Implement the copy constructor and assignment operator when a member (e.g. raw pointer) needs to be explicitly allocated for the assignment to be valid. You'd likely need a destructor as well: Rule off three. Or conversely, if your class is simple enough where it doesn't need a destructor, it probably doesn't need a copy constructor or assignment operator either to be explicitly defined.

Just take those out.

   class SurveyData
   {
       public:
           int   getSector() const;
           int   getExposure() const;
           int   getSpeed() const;
 
           SurveyData();
           SurveyData(int, int, int);
  
       private:
           int sector;
           int exposure;
           int speed;
   };

But if you really need to have a copy constructor or assignment operator, these methods have access to private data. So you can always say:

  SurveyData& SurveyData::operator=(const SurveyData& s)
  {
      sector = s.sector;
      exposure = s.exposure;
      speed = s.speed;
      return *this;
  }

Upvotes: 2

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