http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52282
Bug #: 52282 Summary: [C++0x] ICE / confused by earlier errors with decltype/constexpr Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: andyg1...@hotmail.co.uk The following code causes the compiler problems. The version I am using is gcc 4.7.0-20120210. template <typename T, T V> struct A { static constexpr T a() { return V; } }; template <typename T, T V> struct B { typedef T type; static constexpr type b() { return V; } }; template <typename T, T V> struct C { static constexpr decltype(V) c() { return V; } }; static_assert(A<int, 10>::a() == 10, "oops"); static_assert(B<int, 10>::b() == 10, "oops"); static_assert(C<int, 10>::c() == 10, "oops"); struct D { static constexpr int d() { return 10; } }; static_assert((A<int(*)(), &D::d>::a())() == 10, "oops"); static_assert((B<int(*)(), &D::d>::b())() == 10, "oops"); // line 30 static_assert((C<int(*)(), &D::d>::c())() == 10, "oops"); The code as given above will give the following output: 1.cpp:30:1: error: non-constant condition for static assertion 1.cpp:30:38: error: expression ‘D::d’ does not designate a constexpr function 1.cpp:17: confused by earlier errors, bailing out Commenting out the line 30 will produce an ICE instead: 1.cpp: In instantiation of ‘struct C<int (*)(), D::d>’: 1.cpp:31:34: required from here 1.cpp:17:31: internal compiler error: in finish_decltype_type, at cp/semantics.c:5277 There are two issues here: the first is, of course, the ICE; the second is that gcc is not correctly determining the return type when it is abstracted as in structs B and C and the type is a static function pointer. Note that non-static member function pointers do not generate either issues, although it is necessary to add "const" to the pointer type but not to the corresponding function definition: struct E { constexpr int e() { return 10; } }; constexpr E e; static_assert((e.*A<int(E::*)()const, &E::e>::a())() == 10, "oops"); static_assert((e.*B<int(E::*)()const, &E::e>::b())() == 10, "oops"); static_assert((e.*C<int(E::*)()const, &E::e>::c())() == 10, "oops");