Subject: Re: [boost] Can C++11 INVOKE be defined with C++98 compilers?
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2013-04-12 01:51:22
On Thu, Apr 11, 2013 at 10:41 PM, Vicente J. Botet Escriba <
> Le 12/04/13 06:07, Jeffrey Lee Hellrung, Jr. a Ã©crit :
>> On Tue, Apr 9, 2013 at 11:02 PM, Vicente J. Botet Escriba <
>> vicente.botet_at_[hidden]> wrote:
>>> I would like to implement C++11 INVOKE on C++98 compilers.
>>> I have a C++11 implementation on boost/thread/detail/invoke.hpp based on
>>> the one of libc++.
>>> Could this be done or there is something that can not be done inherently?
>>> Can you briefly describe what INVOKE does (or...should do)?
> from the standard http://www.open-std.org/JTC1/**
> 20.8.2 Requirements [func.require]
> 1 Deï¬ne INVOKE(f, t1, t2, ..., tN) as follows:
> â (t1.*f)(t2, ..., tN) when f is a pointer to a member function of a class
> T and t1 is an object of
> type T or a reference to an object of type T or a reference to an object
> of a type derived from T;
> â ((*t1).*f)(t2, ..., tN) when f is a pointer to a member function of a
> class T and t1 is not one of
> the types described in the previous item;
> â t1.*f when N == 1 and f is a pointer to member data of a class T and t1
> is an object of type T or a
> reference to an object of type T or a reference to an object of a type
> derived from T;
> â (*t1).*f when N == 1 and f is a pointer to member data of a class T and
> t1 is not one of the types
> described in the previous item;
> â f(t1, t2, ..., tN) in all other cases.
> 2 Deï¬ne INVOKE(f, t1, t2, ..., tN, R) as INVOKE(f, t1, t2, ..., tN)
> implicitly converted to R
> The libc++ implementation is
> // __invoke
> // bullets 1 and 2
> template <class _Fp, class _A0, class ..._Args>
> inline _LIBCPP_INLINE_VISIBILITY
> __invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
> -> decltype((_VSTD::forward<_A0>(**__a0).*__f)(_VSTD::forward<_**
> return (_VSTD::forward<_A0>(__a0).*__**f)(_VSTD::forward<_Args>(__**
I glanced at your implementation in thread/detail, and noticed you had
replaced the &&'s with BOOST_THREAD_RV_REF's, which I don't think is right
In C++03, you might be able to get away with defining an INVOKE (variadic)
macro that does what you want...? Hmmm...thinking about it a bit, the
difference between the pointer-to-member-function case and function
object/pointer case makes that tricky.
Maybe the best you can do in C++03 is imperfect forwarding with multiple
overloads for each arity + invokable-type combination :(
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