error on webrtc base/sigslot.h file: error: expected ')' before '...' token void emit(Args... args) const

[Nabi]

Hi everone!
I'm trying to use google webrtc api, but I got some errors on sigslot.h file while compiling project. Error on this class:

class _opaque_connection
	{
	private:
		typedef void (*emit_t)(const _opaque_connection*);
		template< typename FromT, typename ToT >
		union union_caster
		{
			FromT from;
			ToT to;
		};

		emit_t pemit;
		has_slots_interface* pdest;
		// Pointers to member functions may be up to 16 bytes for virtual classes,
		// so make sure we have enough space to store it.
		unsigned char pmethod[16];

	public:
		template< typename DestT, typename ... Args >
		_opaque_connection(DestT* pd, void (DestT::*pm)(Args...)) : pdest(pd)
		{
			typedef void (DestT::*pm_t)(Args...);
			static_assert(sizeof(pm_t) <= sizeof(pmethod), "Size of slot function pointer too large.");

			std::memcpy(pmethod, &pm, sizeof(pm_t));

			typedef void (*em_t)(const _opaque_connection* self, Args...);
			union_caster< em_t, emit_t > caster2;
			caster2.from = &_opaque_connection::emitter< DestT, Args... >;
			pemit = caster2.to;
		}

		has_slots_interface* getdest() const { return pdest; }

		_opaque_connection duplicate(has_slots_interface* newtarget) const
		{
			_opaque_connection res = *this;
			res.pdest = newtarget;
			return res;
		}

		// Just calls the stored "emitter" function pointer stored at construction
		// time.
		template< typename ... Args >
		void emit(Args... args) const
		{
			typedef void (*em_t)(const _opaque_connection*, Args...);
			union_caster< emit_t, em_t > caster;
			caster.from = pemit;
			(caster.to)(this, args...);
		}

	private:
		template< typename DestT, typename ... Args >
		static void emitter(const _opaque_connection* self, Args... args)
		{
			typedef void (DestT::*pm_t)(Args...);
			pm_t pm;
			std::memcpy(&pm, self->pmethod, sizeof(pm_t));
			(static_cast< DestT* >(self->pdest)->*(pm))(args...);
		}
	};

error:

expected ')' before '...' token
   void emit(Args... args) const
                 ^

what is wrong?
HELP

[VRonin]

Don't know what this has to do with Qt but I suppose it might be a naming clash, see http://doc.qt.io/qt-5/signalsandslots.html#using-qt-with-3rd-party-signals-and-slots

[JonB]

@Nabi
You have line:

void emit(Args... args) const

in your code. I'm not a C++ expert, but is that really legal?

Alternatively, if you are posting here because you have also included Qt header files into your source file, be aware that Qt defines, I believe, an emit as a macro (which expands to nothing, I think), and that just might be interfering with the emit() you have here?

[SGaist]

@JonB Yes it is. See parameter pack.

[JonB]

@SGaist
C++ is getting (even more) ridiculous then!

So given OP's compiler error message, what's wrong then?! Wrong compiler C++ version? emit defined as a macro by Qt if OP has included a Qt header file, since he's posting on a Qt forum? C++ just feeling grumpy/having a bad-hair day?

[jsulm]

@JonB Yes, I think he simply has a naming clash as @VRonin already suggested, not C++ issue :-)