[Bug c++/65299] Inheriting from two classes with increment operators
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65299 Andrew Pinski changed: What|Removed |Added Status|UNCONFIRMED |RESOLVED Resolution|--- |INVALID --- Comment #6 from Andrew Pinski --- So clang bug and not a GCC bug.
[Bug c++/65299] Inheriting from two classes with increment operators
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65299 --- Comment #4 from Im ieee ieee at bk dot ru --- (In reply to Jonathan Wakely from comment #3) My initial reaction is that GCC and ICC/EDG are correct. Name lookup is performed for operator++ and if a name is found in two different base classes the result is ambiguous. The different argument lists are not considered until after name lookup. Isn't the int parameter a special case, because it is used to differentiate between prefix and postfix increment operators? And there is no other difference between their declarations.
[Bug c++/65299] Inheriting from two classes with increment operators
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65299
--- Comment #5 from Jonathan Wakely redi at gcc dot gnu.org ---
[over.match.oper] says c++ does name lookup for operator++ using qualified
lookup for C::operator++ and unqualified lookup for operator++ (and the
built-in candidates, which aren't valid here). If name lookup succeeds, it
performs overload resolution, then calls the function with 0 for the int
parameter ([over.inc] When the postfix increment is called as a result of
using the ++ operator, the int argument will have value zero.)
If you change your program to do that explicitly:
C c;
c.C::operator++(0);
c.C::operator++();
Then Clang agrees that the call is ambiguous.
c.cc:18:10: error: member 'operator++' found in multiple base classes of
different types
c.C::operator++(0);
^
c.cc:3:8: note: member found by ambiguous name lookup
A operator++(){return *this;}
^
c.cc:8:7: note: member found by ambiguous name lookup
B operator++(int){return *this;}
^
1 error generated.
I don't see why Clang behaves differently for the ++c and c++ cases, but I
think it's a Clang bug.
[Bug c++/65299] Inheriting from two classes with increment operators
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65299 --- Comment #1 from Jonathan Wakely redi at gcc dot gnu.org --- EDG rejects it for the same reason as GCC: c.cc, line 20: error: more than one operator ++ matches these operands: C::operator++ (ambiguous by inheritance) operand types are: C ++ c++; ^ c.cc, line 21: error: more than one operator ++ matches these operands: C::operator++ (ambiguous by inheritance) operand types are: ++ C ++c; ^
[Bug c++/65299] Inheriting from two classes with increment operators
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65299 --- Comment #2 from Im ieee ieee at bk dot ru --- I have a mistake, ICC also rejects the code: C::operator++ (ambiguous by inheritance) operand types are: C ++ c++; ^
[Bug c++/65299] Inheriting from two classes with increment operators
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65299 --- Comment #3 from Jonathan Wakely redi at gcc dot gnu.org --- My initial reaction is that GCC and ICC/EDG are correct. Name lookup is performed for operator++ and if a name is found in two different base classes the result is ambiguous. The different argument lists are not considered until after name lookup.
