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Use BOOST_EXPLICIT_OPERATOR_BOOL for optional

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I often have the problem that when I change a std::wstring to boost::optional<std::wstring> and the variable is used as a parameter with Boost.Format, the result silently changes from the string contents to "1".

This change prevents implicit conversion to bool if the compiler supports explicit conversion operators.
This commit is contained in:
Marcel Raad
2014-04-24 10:00:43 +02:00
committed by Andrzej Krzemienski
parent b4738ac07e
commit c7cf80e5df
8 changed files with 46 additions and 23 deletions
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15
include/boost/optional/optional.hpp
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@ -36,6 +36,7 @@
#include <boost/utility/addressof.hpp>
#include <boost/utility/compare_pointees.hpp>
#include <boost/utility/in_place_factory.hpp>
#include <boost/utility/explicit_operator_bool.hpp>
#include <boost/optional/optional_fwd.hpp>
@ -180,8 +181,6 @@ class optional_base : public optional_tag
typedef BOOST_DEDUCED_TYPENAME mpl::if_<is_reference_predicate,types_when_ref,types_when_not_ref>::type types ;
protected:
typedef bool (this_type::*unspecified_bool_type)() const;
typedef BOOST_DEDUCED_TYPENAME types::reference_type reference_type ;
typedef BOOST_DEDUCED_TYPENAME types::reference_const_type reference_const_type ;
typedef BOOST_DEDUCED_TYPENAME types::pointer_type pointer_type ;
@ -418,8 +417,6 @@ class optional_base : public optional_tag
destroy_impl(is_reference_predicate()) ;
}
unspecified_bool_type safe_bool() const { return m_initialized ? &this_type::is_initialized : 0 ; }
reference_const_type get_impl() const { return dereference(get_object(), is_reference_predicate() ) ; }
reference_type get_impl() { return dereference(get_object(), is_reference_predicate() ) ; }
@ -479,8 +476,6 @@ class optional : public optional_detail::optional_base<T>
{
typedef optional_detail::optional_base<T> base ;
typedef BOOST_DEDUCED_TYPENAME base::unspecified_bool_type unspecified_bool_type ;
public :
typedef optional<T> this_type ;
@ -620,13 +615,9 @@ class optional : public optional_detail::optional_base<T>
reference_const_type operator *() const { return this->get() ; }
reference_type operator *() { return this->get() ; }
// implicit conversion to "bool"
// No-throw
operator unspecified_bool_type() const { return this->safe_bool() ; }
// This is provided for those compilers which don't like the conversion to bool
// on some contexts.
bool operator!() const { return !this->is_initialized() ; }
BOOST_EXPLICIT_OPERATOR_BOOL()
} ;
// Returns optional<T>(v)