When compiling the following code using C++11 options: -Wall -Wextra -std=c++11 -pedantic or using C++1y options: -Wall -Wextra -std=c++1y -pedantic it is accepted by clang 3.5 trunk 208701 or 3.4 final: //--------------------- template<class T> struct add_ptr { using type = T*; }; int main() { using FC = void () const; using PFC = add_ptr<FC>::type; using FLR = void () &; using PFLR = add_ptr<FLR>::type; using FRR = void () &&; using PFRR = add_ptr<FRR>::type; } //--------------------- After resolution of CWG 1417, http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1417 the formation of a pointer to function types with cv-qualifier or ref-qualifier (even in template context) is not supported. In non-template context, clang already rejects such an attempt. The code had been compiled using the online-compiler http://melpon.org/wandbox/ therefore the provided information about OS and hardware are guesses on my side.
Fixed in r208825, but I'm leaving this open because we're not done here yet. We still incorrectly accept these: template<typename T> struct S { void f(T); }; S<void () const> s1; S<void () &> s2; ... because we don't properly validate the pointer type we build when performing function-to-pointer decay.
(In reply to comment #1) > Fixed in r208825, but I'm leaving this open because we're not done here yet. > We still incorrectly accept these: > > template<typename T> struct S { > void f(T); > }; > S<void () const> s1; > S<void () &> s2; > > ... because we don't properly validate the pointer type we build when > performing function-to-pointer decay. Good afternoon, so, in the context of this question I would like to clarify, that this rule (8.3.1/4): "Forming a reference to function type is ill-formed if the function type has cv-qualifiers or a ref-qualifier" applicable for this code: #include <iostream> template <typename F> void (* test()) (F); template <typename X> char (& probe( void(*) ( X * ) ) )[1]; template <typename X> char (& probe( void(*) ( X ) ) )[2]; int main() { std::cout << sizeof(probe(test<void() const>())); } in context of C++14 standard (for versions 3.4 and earlier this code prints "1", 3.5 and higher prints "2")? And what about C++03 (in which there is no explicit limitation)? Behaviour whould same, or not?