struct A
{
  A(int)
  { }
};

template<class T>
struct B
{
  T t;
  // Error: cannot find constructor for class matching A::A()
};

int main()
{
  B<A> *a = 0;
  B<A> b(*a);

  return 0;
}


There is no need trying to instantiate the default constructor for B<A>. From Boosts regex++ library (low priority).


bye, Christof

-- 
http://cmeerw.org                                 JID: cmeerw@jabber.at mailto cmeerw at web.de

...and what have you contributed to the Net?

I'm mystified how this can work. How can any instance of B<A> be created?

"Christof Meerwald" <cmeerw@web.de> wrote in message news:av264i$ub6$2@digitaldaemon.com...
> struct A
> {
>   A(int)
>   { }
> };
>
> template<class T>
> struct B
> {
>   T t;
>   // Error: cannot find constructor for class matching A::A()
> };
>
> int main()
> {
>   B<A> *a = 0;
>   B<A> b(*a);
>
>   return 0;
> }
>
>
> There is no need trying to instantiate the default constructor for B<A>. From Boosts regex++ library (low priority).
>
>
> bye, Christof
>
> --
> http://cmeerw.org                                 JID: cmeerw@jabber.at mailto cmeerw at web.de
>
> ...and what have you contributed to the Net?

On Sat, 4 Jan 2003 01:35:12 -0800, Walter wrote:
> I'm mystified how this can work. How can any instance of B<A> be created?

STLport does it this way:

  A a(0);

  B<A> *b1 = (B<A> *) malloc(sizeof(B<A>));
  new (&b1->t) A(a);


> "Christof Meerwald" <cmeerw@web.de> wrote in message news:av264i$ub6$2@digitaldaemon.com...
>> struct A
>> {
>>   A(int)
>>   { }
>> };
>>
>> template<class T>
>> struct B
>> {
>>   T t;
>>   // Error: cannot find constructor for class matching A::A()
>> };
[...]


bye, Christof

-- 
http://cmeerw.org                                 JID: cmeerw@jabber.at mailto cmeerw at web.de

...and what have you contributed to the Net?

That's working around how C++ is supposed to work. Object instances are only supposed to be built with constructors. Of course, STLport can be easilly fixed by adding the missing constructor. The malloc call below should be replaced with a new().

"Christof Meerwald" <cmeerw@web.de> wrote in message news:av6jqo$eoo$1@digitaldaemon.com...
> On Sat, 4 Jan 2003 01:35:12 -0800, Walter wrote:
> > I'm mystified how this can work. How can any instance of B<A> be
created?
>
> STLport does it this way:
>
>   A a(0);
>
>   B<A> *b1 = (B<A> *) malloc(sizeof(B<A>));
>   new (&b1->t) A(a);
>
>
> > "Christof Meerwald" <cmeerw@web.de> wrote in message news:av264i$ub6$2@digitaldaemon.com...
> >> struct A
> >> {
> >>   A(int)
> >>   { }
> >> };
> >>
> >> template<class T>
> >> struct B
> >> {
> >>   T t;
> >>   // Error: cannot find constructor for class matching A::A()
> >> };
> [...]
>
>
> bye, Christof
>
> --
> http://cmeerw.org                                 JID: cmeerw@jabber.at mailto cmeerw at web.de
>
> ...and what have you contributed to the Net?