Absurd Program Output

Hello all
i tried the following code and got unexpected outputs.
can anyone provide me with any feedback on any mistake that i have done.

Code:

---

#include<iostream.h>
#include<stdio.h>
void stm()
        {
                cout<<"hello";
        }
struct a
        {
                stm();
        }b;
main()
        {
              cout<<endl<<b.stm();
              cout<<endl<<sizeof(b)<<endl;
              stm();
              return(0);
          }

---

:confused:


output :

[

it do not compiles why ?
and on commenting the first cout it gives the value 1.

No such thing as iostream.h, although there is a header called "iostream". Similarly, no such thing as stdio.h, although there is a header "cstdio" -- but you don't need it for this program, since you're not using any functions from that header.
You're missing a namespace std declaration, to use cout and endl without qualification.
You can't call a function inside a struct, and you can't declare a function without giving a return type, so that stm() inside the struct declaration is just wrong.
And finally, struct a contains no members, so sizeof b must be at least zero, but it can be larger.

Code:

---

#include<iostream>
#include<cstdio>

void stm()
{
    std::cout << "hello";
}

struct a
{
    void stm();
}b;

int main()
{
    std::cout << std::endl << b.stm();
    std::cout << std::endl << sizeof(b) << std::endl;
    stm();
    return(0);
}

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You're trying to cout the value of b.stm() which is a function call returning a void, you can't do that.

Quote:

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You can't call a function inside a struct

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Sure you can, ala struct/class member functions. ...not in the way the OP's trying to do it here but it can be done.

Quote:

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And finally, struct a contains no members, so sizeof b must be at least zero, but it can be larger.

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I think "empty" structs need to be at least 1 byte.

Quote:

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Originally Posted by hk_mp5kpdw

Sure you can.

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I think tabstop is referring to the fact that you can't call a function inside a struct declaration (or definition). It must be done inside a function inside the struct - ie the implementation, not in the definition.

Tabstop:

as far as i know if i dont declear any namespace its the default namespace that is taken.
and please google for "c++ headers" you'll be able to find both of them i used .
and i am using "cout" so i think iostream.h would be used atleast.

Quote:

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Originally Posted by hk_mp5kpdw

Sure you can... not in the way the OP's trying to do it here but it can be done.

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Sorry, should have been clearer -- you can't call a function from the definition of a struct -- you can call a method of a struct, I agree.

Quote:

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Originally Posted by C-RaT

as far as i know if i dont declear any namespace its the default namespace that is taken.

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cout is not located in the default namespace, it's located in std. So are any other standard library functions.

Quote:

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and please google for "c++ headers" you'll be able to find both of them i used .

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Who do you believe more? Some old web pages or expert programmers?
Those headers are deprecated and do not exist. They are not standard headers.

Quote:

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and i am using "cout" so i think iostream.h would be used atleast.

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Make that "iostream".

You probably need a more modern compiler. It seems that you are using something that came out before C++ was standardized (end of 1990s).

Here's what your program would look like in C++.

Code:

---

//proper header
#include<iostream>
using namespace std;

void stm()
    {
        cout<<"hello";
    }

struct a
    {
        //functions require explicit return type
        int stm()
        {
            //if you want to keep the same name
            //you have to indicate that you mean the global stm function
            ::stm();
            //if you declare your functions to return something,
            //you actually have to return something
            return 42;
        }
    }b;

//functions require explicit return type
int main()
    {
      cout<<endl<<b.stm();
      cout<<endl<<sizeof(b)<<endl;
      stm();
      return(0);
    }

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