id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
12998	Can't forward single-argument constructors to sinks	steinar+boost@…	Andrey Semashev	"CasparCG has code like this:

```
        class sink_backend : public boost::log::sinks::basic_formatted_sink_backend<char>
        {
                std::function<void(std::string line)> formatted_line_sink_;
        public:
                sink_backend(std::function<void(std::string line)> formatted_line_sink)
                        : formatted_line_sink_(std::move(formatted_line_sink))
                {
                }

                void consume(const boost::log::record_view& rec, const std::string& formatted_message)
                {
                        try
                        {
                                formatted_line_sink_(formatted_message);
                        }
                        catch (...)
                        {
                                std::cerr << ""[sink_backend] Error while consuming formatted message: "" << formatted_message << std::endl << std::endl;
                        }
                }
        };
[…]
        auto sink = boost::make_shared<sink_type>(std::move(formatted_line_sink));
```

This fails with a long spew of template errors, evidently because for single-argument constructors, only variants with named parameters are considered (sync_frontend.hpp, BOOST_LOG_SINK_CTOR_FORWARD_INTERNAL_1). This is a regression from 1.59.0.

Adding a dummy int parameter and setting it to 0 makes the code compile."	Bugs	new	To Be Determined	log	Boost 1.63.0	Problem