question on static member data

[subramanian100in]

consider the following program:

class Test
{
public:
static Test i;
static double d;
int x;
};

Test t;

int main()
{
return 0;
}

This program compiles fine with both g++ and VC++ 2005 Express
Edition. Since I have not used the static data members I do not get
compilation error. My question is, why the compiler doesn't give an
error for not defining the static data members ?

Kindly explain.

Thanks
V.Subramanian

 

[Michael DOUBEZ]

(e-mail address removed), India a écrit :

consider the following program:

class Test
{
public:
static Test i;
static double d;
int x;
};

Test t;

int main()
{
return 0;
}

This program compiles fine with both g++ and VC++ 2005 Express
Edition. Since I have not used the static data members I do not get
compilation error. My question is, why the compiler doesn't give an
error for not defining the static data members ?

Because they are not required to do it.

The error comes from the link phase, not the compilation one. Since the
compilation doesn't require a link with the actual content of the
statics (because they are no used), everything if fine from the linker
point of view.

Michael

 

[Ron Natalie]

consider the following program:

class Test
{
public:
static Test i;
static double d;
int x;
};

Test t;

int main()
{
return 0;
}

This program compiles fine with both g++ and VC++ 2005 Express
Edition. Since I have not used the static data members I do not get
compilation error. My question is, why the compiler doesn't give an
error for not defining the static data members ?

You don't use them anywhere.

 

[Andrey Tarasevich]

...
Since I have not used the static data members I do not get
compilation error. My question is, why the compiler doesn't give an
error for not defining the static data members ?
...

You have already answered your own question. In C++ you can declare
something and still keep it undefined as long as you are not using it in
the way that'd require a definition.