static function definition

[Senthilvel]

Hi all,
I was thinking that all static members(both data members and functions)
should be defined.
I try to use a static function without defining it
1. outside the class - it gives an error and thats is what i expected.
2. inside the class, ie inside another member function, but it compiles.Why
is that??

Does not the compiler need the definition of Init to generate the code for
Foo ???
I looked into the TCPPPL but didn't find an answer...Can somebody kindly
explain where my understanding
goes wrong ???

#include <iostream>

using namespace std;

class A
{
public:
static void Init();
void Foo() { Init(); }
};

int main()
{
A::Init(); --->Gives an error that Init is an unresolved external symbol.
A a;
a.Foo(); ---> Fine,Also gives an error.
return 0;
}


Here is the actual code that started my confusion..


template<class B,class D> class IsDerivedFrom1
{
class No{};

class Yes{ No no[2]; };
public:
static Yes Test(B* pb);
static No Test(...);

public:
enum { Is = sizeof(Test(static_cast<D*>(0))) > sizeof(No) };

};

Is the declaration of Test is enough to resolve the overload in the
initialisation of the
enum value Is ???

Thanks and Best Regards,
Senthilvel.

 

[John Harrison]

Hi all,
I was thinking that all static members(both data members and functions)
should be defined.
I try to use a static function without defining it
1. outside the class - it gives an error and thats is what i expected.
2. inside the class, ie inside another member function, but it compiles.Why
is that??

Does not the compiler need the definition of Init to generate the code for
Foo ???
I looked into the TCPPPL but didn't find an answer...Can somebody kindly
explain where my understanding
goes wrong ???

#include <iostream>

using namespace std;

class A
{
public:
static void Init();
void Foo() { Init(); }
};

int main()
{
A::Init(); --->Gives an error that Init is an unresolved external symbol.
A a;
a.Foo(); ---> Fine,Also gives an error.
return 0;
}


Here is the actual code that started my confusion..


template<class B,class D> class IsDerivedFrom1
{
class No{};

class Yes{ No no[2]; };
public:
static Yes Test(B* pb);
static No Test(...);

public:
enum { Is = sizeof(Test(static_cast<D*>(0))) > sizeof(No) };

};

Is the declaration of Test is enough to resolve the overload in the
initialisation of the
enum value Is ???

Yes it is. If you don't actually call Test, you don't need to define it.

john