Re: [boost] [config] unexpected explicit operators conversion on some compilers.

Subject: Re: [boost] [config] unexpected explicit operators conversion on some compilers.
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2012-04-10 12:39:10

Le 31/03/12 08:49, Vicente J. Botet Escriba a écrit :
> Hi,
>
> Given the following explicit bool conversion
>
>     template<typename Mutex>
>     class unique_lock
>     {
>     public:
>         explicit operator bool() const BOOST_NOEXCEPT
>
> I was expecting the following code to compile fail (note the int cast)
>
>     boost::unique_lock<boost::mutex> lk0;
>     int i = int(lk0);
>
> It fails with gcc-4.7.0, but compile with gcc-4.6.2 and clang-3.0 (I 
> have not tested yet with msvc).
>
> When BOOST_NO_EXPLICIT_CONVERSION_OPERATORS is defined I use the bool 
> safe idiom to emulate the conversion
>
> #if defined(BOOST_NO_EXPLICIT_CONVERSION_OPERATORS)
>         typedef void (unique_lock::*bool_type)();
>         operator bool_type() const BOOST_NOEXCEPT;
>         bool operator!() const BOOST_NOEXCEPT;
> #else
>         explicit operator bool() const BOOST_NOEXCEPT;
> #endif
>
> and in this case the compile fail as desired.
>
> Do we need a new macro to state that even if explicit operators are 
> provide, there are some unexpected conversions that could be introduced?
>
>
Hi,

has anyone some comments on this issue?

Best,
Vicente