Re: [sigc] default constructor needed for R in sigc::slot<R, A1, ...>
- From: Murray Cumming <murrayc murrayc com>
- To: Matthias Langer <mlangc gmx at>
- Cc: libsigc-list gnome org
- Subject: Re: [sigc] default constructor needed for R in sigc::slot<R, A1, ...>
- Date: Thu, 22 Dec 2005 09:42:14 +0100
On Wed, 2005-12-21 at 20:40 +0100, Matthias Langer wrote:
> At least for libsigc++-2.0.15 the return type R in sigc::slot<R, ...>
> needs to be default constructible.
This is probably so that a signal can return a value even when no slots
are connected. But your example uses a slot and no signals, so that
seems unnecessary. But I guess the same code must compile whether or not
the slot is
sigc::slot<NoDefCtor> tSlot(ptr_func(func));
or
sigc::slot<NoDefCtor> tSlot;
And then tSlot() must return something.
> To verify this try
>
> #include <sigc++/slot.h>
> using sigc::slot; using sigc::ptr_fun;
>
> class NoDefCtor
> {
> public:
> NoDefCtor(int dummy) {}
> };
>
> NoDefCtor func()
> { return NoDefCtor(3); }
>
> int main()
> {
> sigc::slot<NoDefCtor> tSlot(ptr_fun(func));
> tSlot();
> }
>
> Now, i don't want to say that this is a bug, but i think it would be
> nicer if the above code fragment compiles ...
>
> Any comments ?
> Matthias
>
>
> _______________________________________________
> libsigc-list mailing list
> libsigc-list gnome org
> http://mail.gnome.org/mailman/listinfo/libsigc-list
--
Murray Cumming
murrayc murrayc com
www.murrayc.com
www.openismus.com
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