[Bug c++/46824] chromium-compile failed because error: no match for ‘operator*’ in

["dodji at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46824

--- Comment #6 from Dodji Seketeli <dodji at gcc dot gnu.org> 2011-03-10 21:20:52 UTC ---
Thank you for reducing this.

Here is what I understand from the reduced test case.

For the expression "*p" the compiler uses overload resolution to
determine which operator "*" to use.  As there is no user provided
operator*() that can take an instance of Ptr in argument, the only
choice left is to consider the built-in operator*() as a viable
candidate for overload resolution.

But then the note in [over.built]/1 says:

    because built-in operators take only operands with non-class type, and
    operator overload resolution occurs only when an operand expression
    originally has class or enumeration type, operator overload resolution
    can resolve to a built-in operator only when an operand has a class type
    that has a user-defined conversion to a non-class type appropriate for
    the operator, or when an operand has an enumeration type that can be
    converted to a type appropriate for the operator.

As there is no user-defined conversion operator that would convert Ptr
into a pointer to native type, the built-in operator*() is not a viable
candidate.

Thus I believe the test case is ill-formed and the user-defined
conversion operator that converts Ptr to Incomplete* seems to be of
little use in this case.

So for the built-in operator to be selected, we'd need e.g, a
user-defined conversion operator Ptr::operator int* ().  Otherwise we'd
need a user-defined operator 'something Ptr::operator*()'.