Re: [boost] [utility] Proposal to extract some components from Boost.Log

Subject: Re: [boost] [utility] Proposal to extract some components from Boost.Log
From: Daryle Walker (darylew_at_[hidden])
Date: 2013-09-01 03:27:06

> Date: Wed, 28 Aug 2013 12:14:51 +0400
> From: andrey.semashev_at_[hidden]
>
> I'd like to extract some general-purpose components from Boost.Log to
> Boost.Utility so that they could be used in other libraries and user's code
> that is not related to logging. The components are mostly standalone
> already and are not tied to Boost.Log specifics.
>
> 1. BOOST_EXPLICIT_OPERATOR_BOOL() macro for defining explicit operator
> bool() for a class. For C++03 compilers the macro implements safe bool
> idiom or just a regular operator bool(), if the compiler doesn't handle
> safe bool well. The generated operator is implemented in terms of
> operator!(), which should be defined for the class:
>
> template< typename T>
> class my_ptr
> {
> T* m_p;
>
> public:
> BOOST_EXPLICIT_OPERATOR_BOOL()
> bool operator! () const
> {
> return !m_p;
> }
> };
>
> Various different implementations of explicit/safe bool operator are
> present in different libraries. It would be good to unify them.
>
> Implementation: boost/log/utility/explicit_operator_bool.hpp
[TRUNCATE]

I could add this to my touch-ups of Boost.Rational, but I see two minor problems using it:

a. It isn't marked "constexpr."  I can add that myself before using "BOOST_EXPLICIT_OPERATOR_BOOL" in "boost/rational.hpp," but what happens if someone corrects it in "explicit_operator_bool.hpp"?  Will the (temporary) double definition cause an error?

b. Its #included Boost.Log-specific configuration header file flags an error if RTTI isn't active.  And it's unconditional, which would make Boost.Rational unusable for small environments that skip RTTI.  But I don't know if Boost.Rational is already unsuitable for such systems, since it uses exceptions and such.

Maybe I'll just make a custom solution for now....

Daryle W.