http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51253
--- Comment #10 from Akim Demaille <akim.demaille at gmail dot com> ---
Well, I have finally found a simple workaround for some of the cases: GCC seems
to be right in the order of evaluation when initializing an array so:
template<int... IS>
int f1()
{
int i = 0;
swallow{ i = 10 * i + IS... };
return i;
}
fails, but
template<int... IS>
int f2()
{
using swallow = int[];
int i = 0;
(void) swallow{ i = 10 * i + IS... };
return i;
}
succeeds. However, GCC's own libstdc++ is exposed to this bug, for instance
make_tuple.
$ cat foo.cc
#include <iostream>
#include <tuple>
struct swallow
{
template<typename... Types>
swallow(Types &&...){}
};
int incr()
{
static int res = 2;
return res++;
}
template<int... IS>
int f1()
{
int i = 0;
swallow{ i = 10 * i + IS... };
return i;
}
template<int... IS>
int f2()
{
using swallow = int[];
int i = 0;
(void) swallow{ i = 10 * i + IS... };
return i;
}
int main()
{
// `i = i * 2 + 2' should be sequenced before `i = i * 3 + 3'
std::cerr << f1<2, 3>() << '\t';
std::cerr << f2<2, 3>() << '\t';
auto t = std::make_tuple(incr(), incr());
std::cerr << std::get<0>(t) << std::get<1>(t) << '\n';
}
$ ./a.32
23 23 23
$ ./a.33
23 23 23
$ ./a.34
23 23 23
$ ./a.35
23 23 23
$ ./a.48
32 23 32
$ ./a.49
32 23 32
where 32...35 is clang++, and 48,49 is gcc.
