The following code does not compile in clang 3.5+, but compiles in all gcc versions and clang < 3.5.
struct Logger {
template <class T>
Logger& operator<<(const T& /*val*/)
{
// m_buf << val;
return *this;
}
};
struct Value {
template <class Stream>
friend Stream& operator<<(Stream& os, const Value& /*val*/)
{
// os << m_val;
return os;
}
};
int main()
{
Logger logger;
Value value;
logger << value;
return 0;
}
The clang error is
<source>:23:12: error: use of overloaded operator '<<' is ambiguous (with operand types 'Logger' and 'Value')
logger << value;
~~~~~~ ^ ~~~~~
<source>:3:13: note: candidate function [with T = Value]
Logger& operator<<(const T& /*val*/)
^
<source>:12:20: note: candidate function [with Stream = Logger]
friend Stream& operator<<(Stream& os, const Value& /*val*/)
^
Who is correct according to the standard, clang or gcc? If clang, how do I properly write a logger with "<<" that redirects any value supporting "<<" to another stream?
