"Peter de Leeuw van Weenen" <pleforum@orion.nl> writes:

>What is the lifetime of a static variable defined in a member function of a
>class? Is it equal to the lifetime of the class, or is it equal to the
>lifetime of the program?

The lifetime of a static variable begins when the flow of control
first passes through its definition, and ends with the end of the
program.

Example:

class T { ... void f(int); };

class U { ... };

void T::f(int i)
{
    if( i > 0) {
 static U u(args);
    }
}

If T::f is never called, or is never called with a positive value,
its local static variable u is never created (and of course never
destroyed).

The first time T::f is called (on behalf of any T object) with
a positive value, its local static variable u is created. It will
be destroyed automatically at program end, as part of exit
processing.

Details of the order of destruction of static objects at program end
are complicated. It's a good idea to write your program so that the
exact point of destruction during exit processing doesn't matter.

--
Steve Clamage, stephen.clamage@sun.com


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On 14 Oct 1999 16:35:39 GMT, "Peter de Leeuw van Weenen"
<pleforum@orion.nl> wrote:

> What is the lifetime of a static variable defined in a member function of a
> class? Is it equal to the lifetime of the class, or is it equal to the
> lifetime of the program?

> I can test it with my C++ compiler, but I want to know if this is formalized
> in the lanquage?

9.4.2 Static data members [class.static.data]

  3 [Note: once the static data member has been defined, it exists even
     if no objects of its class have been created. [Example: in the
     example above, run_chain and running exist even if no objects of
     class process are created by the program. ]]

       class process {
               static process* run_chain;
               static process* running;
       };


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On 14 Oct 1999 16:35:39 GMT, "Peter de Leeuw van Weenen"
<pleforum@orion.nl> wrote:

> What is the lifetime of a static variable defined in a member function of a
> class? Is it equal to the lifetime of the class, or is it equal to the
> lifetime of the program?

> I can test it with my C++ compiler, but I want to know if this is formalized
> in the lanquage?

Ah, you mean a static local variable in a member function of a class
(and not a static data member of the, as I mistakenly assumed in my
previous post)

I think the following general paragraphs apply in this case, too:

3.7.1 Static storage duration [basic.stc.static]

  4 The keyword static can be used to declare a local variable with
    static storage duration. [Note: {...} 3.6.3 describes the
    destruction of local static variables. ]

3.6.3 Termination [basic.start.term]

  1 Destructors for initialized objects of static storage duration
    (declared at block scope or at namespace scope) are called as a
    result of returning from main and as a result of calling exit.

And specifically regarding member functions:

9.3 Member functions [class.mfct]

  6 A static local variable in a member function always refers to the
    same object, whether or not the member function is inline.

Would it be correct to say that the only difference between a static
data member of a class and a local static variable defined in one of the
class' member functions is that latter is only visible inside its
defining block (regarding storage duration, or in every aspect)?


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Peter de Leeuw van Weenen wrote:

> Hello ,
>
> Please, can someone answer the question:
>
> What is the lifetime of a static variable defined in a member function of a
> class? Is it equal to the lifetime of the class, or is it equal to the
> lifetime of the program?
>
> I can test it with my C++ compiler, but I want to know if this is formalized
> in the lanquage?
>

"static" variables persist for the duration of the program.

Regards,
Matt Frantz
Micron Tech. TX


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In article <7u44td$1lk5$1@buty.wanadoo.nl>,
  "Peter de Leeuw van Weenen" <pleforum@orion.nl> wrote:
>
> Hello ,
>
> Please, can someone answer the question:
>
> What is the lifetime of a static variable defined in a member function
> of a
> class? Is it equal to the lifetime of the class, or is it equal to the
> lifetime of the program?
The lifetime of the program.  The variable has "static storage
duration", which is independent of whether or not the variable is a
member function.

--
Jim
I ignore all email from recruitment agencies.
Please do not send me email with questions - post
here.


Sent via Deja.com http://www.deja.com/
Before you buy.


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Daniel Hartmeier wrote:

> On 14 Oct 1999 16:35:39 GMT, "Peter de Leeuw van Weenen"
> <pleforum@orion.nl> wrote:
>
> > What is the lifetime of a static variable defined in a member function of a
> > class? Is it equal to the lifetime of the class, or is it equal to the
> > lifetime of the program?
>
> [snip]
>
> Would it be correct to say that the only difference between a static
> data member of a class and a local static variable defined in one of the
> class' member functions is that latter is only visible inside its
> defining block (regarding storage duration, or in every aspect)?

The static variables defined in a member function are initialized the first time
they go into scope.  Static data members are initialized at startup.

Regards,
Matt Frantz
Micron Tech. TX



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Hello ,

Please, can someone answer the question:

What is the lifetime of a static variable defined in a member function of a
class? Is it equal to the lifetime of the class, or is it equal to the
lifetime of the program?

I can test it with my C++ compiler, but I want to know if this is formalized
in the lanquage?

Peter de Leeuw
Software Engineer
pleforum@orion.nl




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