Does std::cout have a return value?
Because the operands of cout << cout
are user-defined types, the expression is effectively a function call. The compiler must find the best operator<<
that matches the operands, which in this case are both of type std::ostream
.
There are many candidate operator overloads from which to choose, but I'll just describe the one that ends up getting selected, following the usual overload resolution process.
std::ostream
has a conversion operator that allows conversion to void*
. This is used to enable testing the state of the stream as a boolean condition (i.e., it allows if (cout)
to work).
The right-hand operand expression cout
is implicitly converted to void const*
using this conversion operator, then the operator<<
overload that takes an ostream&
and a void const*
is called to write this pointer value.
Note that the actual value resulting from the ostream
to void*
conversion is unspecified. The specification only mandates that if the stream is in a bad state, a null pointer is returned, otherwise a non-null pointer is returned.
The operator<<
overloads for stream insertion do have a return value: they return the stream that was provided as an operand. This is what allows chaining of insertion operations (and for input streams, extraction operations using >>
).
cout
does not have a return value. cout
is an object of type ostream
. operator <<
has a return value, it returns a reference to cout
.
See http://www.cplusplus.com/reference/iostream/ostream/operator%3C%3C/ for reference.
The only signature that matches is:
ostream& operator<< (ostream& ( *pf )(ostream&));
so it returns the pointer to the operator<<
member.
the one in James' answer. :)
I believe that would be the address of the ostream object that "" got printed to