Error While Compiling this C++ code

Question

I got the following error wwhile compiling this c++ code . What can be the reason behind this ?

     # include <iostream>
     # include <stdio.h>
     # include <conio.h>

     using namespace std;

     class Foo
     {
      int a;
      public :
      virtual void Fun1(); 

      Foo()
      {a=5;}
     };

     Class X: public Foo   // Error class does not name a type
     {
      Foo f;
      public:
      void Fun1() { }       
      X()
      {
       memset(&f,0x0,sizeof(f));
      }
     };

     int main()
     {
      X x; // Error 'X undeclared and expected ; before x, i guess because of first one
      getch();
      return 0;
      }

Mike Seymour · Accepted Answer · 2012-02-16 17:42:55Z

2

The keyword class begins with a lower-case c. That will fix the errors you reported, but more errors remain.

You declare Foo::Fun1, but don't define it.

Finally you'll need to include <cstring> for the declaration of std::memset. It's possible that another header is including it indirectly, but you can't rely on that.

You'll then have undefined runtime behaviour, since it's not valid to use memset to overwrite non-POD objects - Foo has a virtual function, and so is not POD.

edited Feb 16, 2012 at 17:42

answered Feb 16, 2012 at 17:29

Mike Seymour

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6 Comments

Invictus Over a year ago

I corrected the case error but still While Compiling i get some linker error . Is it due to memset code that i am using ? Can you explain that . I have also defined the Fun1() {cout << "LOL" ;} in class X but still compilation error.

Mike Seymour Over a year ago

There shouldn't be a link error if you've defined Foo::Fun1. What is the error exactly?

Mike Seymour Over a year ago

@Ritesh: You'll get that error if you haven't defined Foo::Fun1 (or perhaps if there's another virtual function that you haven't defined). Are you sure you've defined it?

Invictus Over a year ago

I guess your answer :-You'll then have undefined runtime behaviour, since it's not valid to use memset to overwrite non-POD objects - Foo has a virtual function, and so is not POD. Is very correct the only thing is me getting a compiler linking error instead of Run time error

Mike Seymour Over a year ago

@Ritesh: I just noticed in your first comment, you say you defined X::Fun1. You need to define Foo::Fun1 as well to fix the link error.

|

sholsapp · Accepted Answer · 2012-02-16 17:27:55Z

2

The Class should be class.

answered Feb 16, 2012 at 17:27

sholsapp

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Comments

simont · Accepted Answer · 2012-02-16 17:29:16Z

1

Class X: public Foo should be class X: public Foo, which should fix both errors.

answered Feb 16, 2012 at 17:29

simont

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Bojan Komazec · Accepted Answer · 2012-02-16 17:30:24Z

1

C++ language is case sensitive and requires its keywords to be written in lowercase. class is valid C++ keyword but Class is not. Rename Class to class when declaring class X.

answered Feb 16, 2012 at 17:30

Bojan Komazec

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Boris Strandjev · Accepted Answer · 2012-02-16 17:28:28Z

0

Class X is named with capital C. This is the problem.

answered Feb 16, 2012 at 17:28

Boris Strandjev

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macduff · Accepted Answer · 2012-02-16 17:31:05Z

0

Your error really starts with the: Class X: public Foo // Error class does not name a type Class must be class.

answered Feb 16, 2012 at 17:31

macduff

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