http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57765
Bug ID: 57765
Summary: [C++11] Variadic Template Specialization does not
follow the INCITS/ISO/IEC 14882-2011 standard
Product: gcc
Version: 4.8.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: aaronngray.lists at gmail dot com
Prompted by a Stack Overflow article :-
http://stackoverflow.com/questions/17332749/vs2013-fails-with-variadic-template-specialization/
There seems to be anomalies between GCC 4.8.1's 0x11 implementation
and the standard.
It shows the code :-
template <typename Sig, Sig& S> struct OpF;
template <typename TR, typename ... Ts, TR (&f)(Ts...)> struct
OpF<TR (Ts...), f> { };
int foo(int x) { return 0; }
OpF<int (int), foo> f;
Given the C++ Standard outlaws this code, see 14.1 paragraphs 11 and 15.
Note that GCC accepts the following code with either -std=gnu++11 or
-std=c++11, the latter should be strict to the standard. Also given
these paragraphs were in the draft C++ standard too.
On the other hand GCC 4.8.1 will not accept a simple trailing 'int'
parameter after a variadic template list.
template < typename TR, typename ... Ts, int i> TR tester(Ts...);
// error: parameter pack ‘Ts’ must be at the end of the template
parameter list
There seems to be quite an inconsistency even in an augmentation to
the standard.
On a personal note both these forms are syntactically correct but not
semantically by the standard, given that this is just a simple type
based pattern matching problem as far as I can see it would be nice to
have it within the language as it seems to fit naturally with
requirements.
