http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55460
Bug #: 55460
Summary: Template-dependent name is not looked up at
instantiation point
Classification: Unclassified
Product: gcc
Version: 4.6.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: solo...@mail.com
Created attachment 28768
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28768
Code reproducing bug
Howdy,
I think this is a bug in G++. I have a call to a template function filter(T) in
a template context. filter() is further overloaded before the instantiation
point. G++ 4.6.1 and 4.5.2 (both under MinGW, sorry, I don't have access to a
more recent version) seems to resolve it at declaration point (see attachment
for the exact code reproducing bug):
namespace my
{
...
// A function template that by default behaves as identity
template <typename P>
typename std::remove_reference<P>::type
filter(P&& p) throw() { return std::move(p); }
...
} // of namespace my
// Since this is unrestricted template, ADL won't work, so we have to stick
// this overloaded operator building an expression template into the global
scope
template <typename P1>
inline auto operator&(P1&& p1) throw()
-> typename std::enable_if<
my::is_mine<P1>::value,
my::address<decltype(my::filter(std::forward<P1>(p1)))>
>::type
{
// NOTE: call to filter depends on template argument, thus have to be
// resolved at instantiation point. But it doesn't!
return my::address<decltype(my::filter(std::forward<P1>(p1)))>
(my::filter(std::forward<P1>(p1)));
}
// We now declare few more classes modeling our concept: var and ref
namespace my
{
template <typename T> class var;
template <typename T> class ref;
...
// and specialize function filter on them
template <typename T> inline ref<var<T>> filter( var<T>& t) throw()
{ return ref<var<T>>(t); }
} // of namespace my
int main()
{
my::var<int> h;
auto&& a = &h; // Instantiate expression template via overloaded operator&
std::cout << typeid(a).name() << std::endl;
}
GCC 4.6.1 output is:
N2my7addressINS_3varIiEEEE
which indicates that there is no ref<> applied to var<> in instantiation of
address<>. Visual C++ 10 and 11 produce:
struct my::address<struct my::ref<struct my::var<int> > >
which have ref<> in between and is what I was actually expecting to have.
If I move the definition of overloaded operator& after the second namespace my
is closed, the ref<> does properly appear on top of the var<>.
Can you please have a look at this?
Thank you!
