Which function is used to initialize the static class member?

Question

I have a question about which function is chosen to init a static class member.

//Base.h

class Base
{
private:
    static int count;
    static int countInit()
    {
        return 10;
    }
public:
    Base()
    {
    }
};

//and Base.cpp
static int countInit()
{
    return 0;
}
int Base::count=countInit();//member function is used.
static int local_count=countInit();//the local one in Base.cpp

The variable Base::count is initialized with Base::countInit() rather than the countInit() defined in Base.cpp. But the local_count is initialized by the local countInit. So, I wonder, is there a rule like Koenig lookup within this case?

@LuchianGrigore, Yes, it does. I wasn't aware that happened. — chris, Jul 17 '13 at 09:26
where is "int Base::count=countInit();" invoked ? cause static member function Base::countInit() count not be invoked only by countInit() out of the scope of class Base. — lulyon, Jul 17 '13 at 09:42
@NeilKirk if call the ::countInit(), the local countInit is used. — Donglei, Jul 17 '13 at 11:46

score 17 · Accepted Answer · edited Jul 17 '13 at 11:57

After you write int Base::count you are in class Base, so static function of class will be called. Unqualified lookup will be used here

from 3.4.2/13

A name used in the definition of a static data member of class X (9.4.2) (after the qualified-id of the static member) is looked up as if the name was used in a member function of X.

from 9.4.2

The definition for a static data member shall appear in a namespace scope enclosing the member’s class definition. In the definition at namespace scope, the name of the static data member shall be qualified by its class name using the :: operator. The initializer expression in the definition of a static data member is in the scope of its class

Example:
class process {
static process* run_chain;
static process* running;
};
process* process::running = get_main();
process* process::run_chain = running;

Which function is used to initialize the static class member?

1 Answers1