From 7da193fde1a9c1bc925ee980339f4df2e1a66fa7 Mon Sep 17 00:00:00 2001

From: Andrey Semashev <andrey.semashev@gmail.com>

Date: Sun, 23 Aug 2015 17:27:20 +0300

Subject: [PATCH] Fixed compilation of operator<< into a record ostream, when

 the operator right hand argument is not directly supported by

 formatting_ostream. Fixed #11549.

---

diff --git a/include/boost/log/sources/record_ostream.hpp b/include/boost/log/sources/record_ostream.hpp

index b3c58e2..c1e8059 100644

--- a/include/boost/log/sources/record_ostream.hpp

+++ b/include/boost/log/sources/record_ostream.hpp

@@ -39,6 +39,18 @@ namespace boost {

 BOOST_LOG_OPEN_NAMESPACE

+template< typename CharT >

+class basic_record_ostream;

+

+namespace aux {

+

+template< typename StreamT, typename R >

+struct enable_if_record_ostream {};

+template< typename CharT, typename R >

+struct enable_if_record_ostream< basic_record_ostream< CharT >, R > { typedef R type; };

+

+} // namespace aux

+

 /*!

  * \brief Logging record adapter with a streaming capability

  *

@@ -174,6 +186,55 @@ typedef basic_record_ostream< char > record_ostream;        //!< Convenience typ

 typedef basic_record_ostream< wchar_t > wrecord_ostream;    //!< Convenience typedef for wide-character logging

 #endif

+// Implementation note: these operators below should be the least attractive for the compiler

+// so that user's overloads are chosen, when present. We use function template partial ordering for this purpose.

+// We also don't use perfect forwarding for the right hand argument because in ths case the generic overload

+// would be more preferred than the typical one written by users:

+//

+// record_ostream& operator<< (record_ostream& strm, my_type const& arg);

+//

+// This is because my_type rvalues require adding const to the type, which counts as a conversion that is not required

+// if there is a perfect forwarding overload.

+template< typename StreamT, typename T >

+inline typename boost::log::aux::enable_if_record_ostream< StreamT, StreamT& >::type

+operator<< (StreamT& strm, T const& value)

+{

+    typedef basic_formatting_ostream< typename StreamT::char_type > formatting_ostream_type;

+    static_cast< formatting_ostream_type& >(strm) << value;

+    return strm;

+}

+

+template< typename StreamT, typename T >

+inline typename boost::log::aux::enable_if_record_ostream< StreamT, StreamT& >::type

+operator<< (StreamT& strm, T& value)

+{

+    typedef basic_formatting_ostream< typename StreamT::char_type > formatting_ostream_type;

+    static_cast< formatting_ostream_type& >(strm) << value;

+    return strm;

+}

+

+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)

+

+template< typename StreamT, typename T >

+inline typename boost::log::aux::enable_if_record_ostream< StreamT, StreamT& >::type

+operator<< (StreamT&& strm, T const& value)

+{

+    typedef basic_formatting_ostream< typename StreamT::char_type > formatting_ostream_type;

+    static_cast< formatting_ostream_type& >(strm) << value;

+    return strm;

+}

+

+template< typename StreamT, typename T >

+inline typename boost::log::aux::enable_if_record_ostream< StreamT, StreamT& >::type

+operator<< (StreamT&& strm, T& value)

+{

+    typedef basic_formatting_ostream< typename StreamT::char_type > formatting_ostream_type;

+    static_cast< formatting_ostream_type& >(strm) << value;

+    return strm;

+}

+

+#endif // !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)

+

 namespace aux {

 //! Internal class that provides formatting streams for record pumps

diff --git a/include/boost/log/utility/formatting_ostream.hpp b/include/boost/log/utility/formatting_ostream.hpp

index 4345206..744acc0 100644

--- a/include/boost/log/utility/formatting_ostream.hpp

+++ b/include/boost/log/utility/formatting_ostream.hpp

@@ -779,6 +779,13 @@ void basic_formatting_ostream< CharT, TraitsT, AllocatorT >::aligned_write(const

 // Implementation note: these operators below should be the least attractive for the compiler

 // so that user's overloads are chosen, when present. We use function template partial ordering for this purpose.

+// We also don't use perfect forwarding for the right hand argument because in ths case the generic overload

+// would be more preferred than the typical one written by users:

+//

+// formatting_ostream& operator<< (formatting_ostream& strm, my_type const& arg);

+//

+// This is because my_type rvalues require adding const to the type, which counts as a conversion that is not required

+// if there is a perfect forwarding overload.

 template< typename StreamT, typename T >

 inline typename boost::log::aux::enable_if_formatting_ostream< StreamT, StreamT& >::type

 operator<< (StreamT& strm, T const& value)