Re: [boost] [1.39.0][Signals2] Release branch test failures

Subject: Re: [boost] [1.39.0][Signals2] Release branch test failures
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2009-04-13 15:08:58

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On Monday 13 April 2009, Peter Dimov wrote:
>
> I haven't. What seems to be happening is that when you pass _1, which is
>
>     inline arg<1> _1() { .. }
>
> to A1 const& a1, A1 is properly deduced as a function type, but the const
> is not dropped, as it should be; instead, the type of a1 becomes arg<1>
> (&)() const (which is illegal BTW). When this a1 is passed (by value) to
> boost::bind, it decays to its corresponding pointer type, arg<1> (*)()
> const - which is also illegal. :-)
>
> A workaround is to use pass by value instead of A1 const&.

Yes, that seems to fix it.  If it is at all helpful, I've attached a more 
minimal test program that triggers the bug with g++ 4.0.1 (compiles fine with 
g++ 4.3.2).  Changing the placeholder to be passed by value makes the compile 
error go away.
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// Copyright (C) Frank Mori Hess 2009

// Use, modification and
// distribution is subject to the Boost Software License, Version
// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

#include <boost/bind.hpp>
#include <boost/function.hpp>

template<typename F, typename A1>
        void binder_template(const F &func,
                const A1 &arg1
// forwarding arg1 by value instead of as a const reference fixes compile error on gcc 4.0.1
//		A1 arg1
        )
{
        boost::function1<int, int> x = boost::bind(func, arg1);
}

int f(int x)
{
        return x;
}

int main()
{
        binder_template(&f, _1);

  return 0;
}

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