Boost C++ Libraries: Ticket #3645: iterator_facade does not work in presence of ::implicit_cast

attachment set

romanp@… — Thu, 19 Nov 2009 17:21:35 GMT

attachment → minimal_boost.cc

Minimal test case demonstrating compilation errors

attachment set

romanp@… — Thu, 19 Nov 2009 17:22:11 GMT

attachment → minimal_no_boost.cc

Minimal test case without boost demonstrating compilation errors

attachment set

romanp@… — Thu, 19 Nov 2009 17:22:46 GMT

attachment → iterator_facade.patch

Patch (qualify call to implicit_cast in iterator_facade.hpp)

cc changed

roman.perepelitsa@… — Thu, 19 Nov 2009 17:32:12 GMT

cc roman.perepelitsa@… added

romanp@… — Thu, 19 Nov 2009 18:04:41 GMT

The compiler is right to complain about ambiguity.

14.8.1 - Explicit template argument specification [temp.arg.explicit]

-6- [Note: For simple function names, argument dependent lookup (basic.lookup.koenig) applies even when the function name is not visible within the scope of the call. This is because the call still has the syntactic form of a function call (basic.lookup.unqual). But when a function template with explicit template arguments is used, the call does not have the correct syntactic form unless there is a function template with that name visible at the point of the call. If no such name is visible, the call is not syntactically well-formed and argument-dependent lookup does not apply. If some such name is visible, argument dependent lookup applies and additional function templates may be found in other namespaces. [Example:

namespace A {

struct B { }; template<int X> void f(B);

} namespace C {

template<class T> void f(T t);

} void g(A::B b) {

f<3>(b); ill-formed: not a function call A::f<3>(b); well-formed C::f<3>(b); ill-formed; argument dependent lookup

only applies to unqualified names

using C::f; f<3>(b); well-formed because C::f is visible; then

A::f is found by argument dependent lookup

}

--- end example] --- end note]

Which means that iterator_facade has unintended point of extension (ADL enabled call).

component changed; owner set

Steven Watanabe — Fri, 20 Nov 2009 03:20:24 GMT

owner set to Dave Abrahams
component None → iterator

romanp@… — Fri, 27 Nov 2009 09:31:52 GMT

David, could you take a look?

In Google, we had to patch boost locally. It would be great to push the fix upstream.

cc changed

Wed, 02 Dec 2009 04:33:49 GMT

cc jyasskin@… added

owner changed

Marshall Clow — Thu, 06 Jan 2011 23:44:24 GMT

owner changed from Dave Abrahams to Marshall Clow

Marshall Clow — Thu, 06 Jan 2011 23:45:12 GMT

Patch applied in revision [67738]; will wait for tests to cycle before merging to release branch.

status changed; resolution set

Marshall Clow — Sat, 08 Jan 2011 18:46:41 GMT

status new → closed
resolution → fixed

Fix merged to release branch in [67792]