i on gcc 5.3 trying function wrapper code work works fine on clang. here boiled down example:
#include <iostream> using namespace std; template<class sig, sig f> struct functionwrapper; template<class ret, class... args, ret (*func)(args...)> struct functionwrapper<ret(args...), func> { }; static int testfunc(int _a, int _b) { return _a + _b; } int main() { functionwrapper<int(int, int), testfunc> wrapper; return 0; } the error on gcc following:
prog.cpp:9:46: error: 'ret(args ...)' not valid type template non-type parameter struct functionwrapper ^ prog.cpp: in function 'int main()': prog.cpp:20:45: error: 'int(int, int)' not valid type template non-type parameter functionwrapper wrapper;
any ideas how make work on both, clang , gcc?
thanks!
i think gcc bug. according [temp.param]:
a non-type template-parameter of type “array of
t” or of function typetadjusted of type “pointert”.
having ret(args...) template non-type parameter equivalent having ret(*)(args...) template non-type parameter.
note gcc [correctly] compile following example, same idea original version:
static int testfunc(int _a, int _b) { return _a + _b; } template <int f(int, int)> struct foo { }; int main() { foo<testfunc> wrapper; return 0; } as workaround, forcing non-type argument pointer allowed both compilers:
template<class sig, sig* f> struct functionwrapper; template<class ret, class... args, ret (*func)(args...)> struct functionwrapper<ret(args...), func> { }; but don't believe should have been necessary.
