Warnings in FILE input code

Code:

---

#include <iostream>
#include <fstream>
#include <list>

using namespace std;

int main()
{
    int no_of_vertices;
    ifstream fin;

    fin.open("RECTANGLE_GRAPH.txt",ios::in);

    if( !fin )
    {
        cout << "File not found!" << endl;
        return 1;
    }

    fin >> no_of_vertices;

    return 0;
}

---

Code:

---

/usr/include/c++/4.4/fstream||In constructor ‘std::basic_ifstream<_CharT, _Traits>::basic_ifstream() [with _CharT = char, _Traits = std::char_traits<char>]’:|
/usr/include/c++/4.4/fstream|440|warning: will never be executed|
/usr/include/c++/4.4/fstream|440|warning: will never be executed|
/usr/include/c++/4.4/fstream|440|warning: will never be executed|
/usr/include/c++/4.4/fstream|440|warning: will never be executed|
/usr/include/c++/4.4/fstream|441|warning: will never be executed|
/usr/include/c++/4.4/fstream|441|warning: will never be executed|
/usr/include/c++/4.4/bits/basic_ios.h||In constructor ‘std::basic_ios<_CharT, _Traits>::basic_ios() [with _CharT = char, _Traits = std::char_traits<char>]’:|
/usr/include/c++/4.4/bits/basic_ios.h|453|warning: will never be executed|
/usr/include/c++/4.4/istream||In constructor ‘std::basic_istream<_CharT, _Traits>::basic_istream() [with _CharT = char, _Traits = std::char_traits<char>]’:|
/usr/include/c++/4.4/istream|582|warning: will never be executed|
/usr/include/c++/4.4/istream|582|warning: will never be executed|
/usr/include/c++/4.4/istream|582|warning: will never be executed|
/usr/include/c++/4.4/istream|582|warning: will never be executed|
/usr/include/c++/4.4/istream|583|warning: will never be executed|
/usr/include/c++/4.4/istream|583|warning: will never be executed|
/usr/include/c++/4.4/istream||In destructor ‘std::basic_istream<_CharT, _Traits>::~basic_istream() [with _CharT = char, _Traits = std::char_traits<char>]’:|
/usr/include/c++/4.4/istream|102|warning: will never be executed|
/usr/include/c++/4.4/istream|102|warning: will never be executed|
/usr/include/c++/4.4/istream|102|warning: will never be executed|
/usr/include/c++/4.4/fstream||In destructor ‘std::basic_ifstream<_CharT, _Traits>::~basic_ifstream() [with _CharT = char, _Traits = std::char_traits<char>]’:|
/usr/include/c++/4.4/fstream|486|warning: will never be executed|
/usr/include/c++/4.4/fstream|486|warning: will never be executed|
/usr/include/c++/4.4/fstream|486|warning: will never be executed|
/usr/include/c++/4.4/fstream|486|warning: will never be executed|
/usr/include/c++/4.4/fstream|486|warning: will never be executed|
||=== Build finished: 0 errors, 21 warnings ===|

---

Using CODE BLOCKS 10.05 in UBUNTU 10.10. Any help please?

The problem is in your installation of the standard library (which is typically installed with your compiler).

You might want to report the warnings to the supplier of your compiler. My guess - although I don't know - is that your compiler is part of the bundle delivered by default with Ubuntu, although that won't be true if you installed a separate package. So, it would be appropriate to report the concern to the Ubuntu folks in the first instance.

For your work, you can ignore the warnings. "never be executed" simply means some functions contain some additional code, but - because of the logic of those function - there is no way that extra code will be executed.