In article <36C9B136.33137EB9@technologist.com>,
  David R Tribble <dtribble@technologist.com> wrote:
> Biju Thomas wrote:
> >
> > stephen.clamage@sun.com (Steve Clamage) wrote:
> > >
> > > >Are class member function names (e.g. C::f in the example below)
> > > >supposed to be convertible to a pointer to the member function?
> > >
> > > The "&" is required, unlike the rule for non-member functions.
> > >
> > > Some compilers accept C::f as meaning &C::f, but that is a
> > > non-standard extension.
> >
> > Since some compilers support it as an extension, it means that it can
> > be done. Then why not make it a standard? At least, for the sake of
> > symmetry with non-member functions. (The same cannnot be done for
> > member data, but, for member functions, I cannot think of any problem
> > it will create.)
>
> Just because it can be done doesn't mean it should be done.  IMHO,
> an explicit '&' makes the intention of the code more obvious.  And
> it's only a single extra character, after all.  Perhaps there are
> bigger issues when dealing with member function pointers, especially
> when used in combination with templates?

When this issue came up last year, someone posted some legal code which
had a different meaning under this rule. Made a believer out of me.
Unfortunately I can't remember what it did and I don't have time to look
it up...

Perhaps whoever posted it then would be so kind as to post it again.

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Biju Thomas wrote:
>
> stephen.clamage@sun.com (Steve Clamage) wrote:
> >
> > >Are class member function names (e.g. C::f in the example below)
> > >supposed to be convertible to a pointer to the member function?
> >
> > The "&" is required, unlike the rule for non-member functions.
> >
> > Some compilers accept C::f as meaning &C::f, but that is a
> > non-standard extension.
>
> Since some compilers support it as an extension, it means that it can
> be done. Then why not make it a standard? At least, for the sake of
> symmetry with non-member functions. (The same cannnot be done for
> member data, but, for member functions, I cannot think of any problem
> it will create.)

Just because it can be done doesn't mean it should be done.  IMHO,
an explicit '&' makes the intention of the code more obvious.  And
it's only a single extra character, after all.  Perhaps there are
bigger issues when dealing with member function pointers, especially
when used in combination with templates?

-- David R. Tribble, dtribble@technologist.com --
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Dan Yergeau wrote in message <79srme$s0f@antonios.Stanford.EDU>...
> [a.baz wants a pointer to member argument]
>    a.baz(C::f);   // g++ 2.8.1 and egcs-1.1.1 reject this
>                   // g++ 2.7.2.x and CC from Sun SC4.2 accept it

This should be rejected.

5.3.1(3) "A pointer to member is only formed when an explicit & is used ..."
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In article <79tdhd$o0v$1@engnews1.eng.sun.com>,
  stephen.clamage@sun.com (Steve Clamage) wrote:
>
> >Are class member function names (e.g. C::f in the example below)
> >supposed to be convertible to a pointer to the member function?
>
> The "&" is required, unlike the rule for non-member functions.
>
> Some compilers accept C::f as meaning &C::f, but that is a
> non-standard extension.

Since some compilers support it as an extension, it means that it can
be done. Then why not make it a standard? At least, for the sake of
symmetry with non-member functions. (The same cannnot be done for member
data, but, for member functions, I cannot think of any problem it
will create.)

Regards,
Biju Thomas

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Are class member function names (e.g. C::f in the example below)
supposed to be convertible to a pointer to the member function?

I'm trying to figure out if the error below is a bug in g++ or an
actual error in the program (i.e. "&" is required class member
functions).


Thanks in advance,

Dan Yergeau
yergeau@leland.stanford.edu


============================================================================
class C
{
public:
    void f(void);
};

typedef void (*funcPtr)(void);
typedef void (C::* memberFuncPtr)(void);

class A
{
public:
    void bar(funcPtr fp);
    void baz(memberFuncPtr fp);
};

void foo()
{
    A a;
    a.bar(foo);
    a.bar(&foo);
    a.baz(&C::f);
    a.baz(C::f);   // g++ 2.8.1 and egcs-1.1.1 reject this
                   // g++ 2.7.2.x and CC from Sun SC4.2 accept it
}

//t2.cc: In function `void foo()':
//t2.cc:23: no matching function for call to `A::baz (void (C::)())'
//t2.cc:14: candidates are: A::baz(void (C::*)())
============================================================================
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yergeau@antonios.Stanford.EDU (Dan Yergeau) writes:

>Are class member function names (e.g. C::f in the example below)
>supposed to be convertible to a pointer to the member function?

>I'm trying to figure out if the error below is a bug in g++ or an
>actual error in the program (i.e. "&" is required class member
>functions).

The "&" is required, unlike the rule for non-member functions.

Some compilers accept C::f as meaning &C::f, but that is a
non-standard extension.

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


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