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Make unary + operator return by value - we can generate dangling references otherwise.

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[SVN r84863]
This commit is contained in:
John Maddock
2013-06-21 15:58:03 +00:00
parent d9d57d3b02
commit e064bea8a9
1 changed files with 10 additions and 3 deletions
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13
include/boost/multiprecision/detail/et_ops.hpp
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@@ -11,12 +11,19 @@ namespace boost{ namespace multiprecision{
//
// Non-member operators for number:
//
// Unary operators first:
// Unary operators first.
// Note that these *must* return by value, even though that's somewhat against
// existing practice. The issue is that in C++11 land one could easily and legitimately
// write:
// auto x = +1234_my_user_defined_suffix;
// which would result in a dangling-reference-to-temporary if unary + returned a reference
// to it's argument. While return-by-value is obviously inefficient in other situations
// the reality is that no one ever uses unary operator+ anyway...!
//
template <class B, expression_template_option ExpressionTemplates>
inline BOOST_CONSTEXPR const number<B, ExpressionTemplates>& operator + (const number<B, ExpressionTemplates>& v) { return v; }
inline BOOST_CONSTEXPR const number<B, ExpressionTemplates> operator + (const number<B, ExpressionTemplates>& v) { return v; }
template <class tag, class Arg1, class Arg2, class Arg3, class Arg4>
inline BOOST_CONSTEXPR const detail::expression<tag, Arg1, Arg2, Arg3, Arg4>& operator + (const detail::expression<tag, Arg1, Arg2, Arg3, Arg4>& v) { return v; }
inline BOOST_CONSTEXPR const detail::expression<tag, Arg1, Arg2, Arg3, Arg4> operator + (const detail::expression<tag, Arg1, Arg2, Arg3, Arg4>& v) { return v; }
template <class B>
inline detail::expression<detail::negate, number<B, et_on> > operator - (const number<B, et_on>& v)
{