Yep, looks like a compiler bug. Reduced (see below) and filed as VSO#445619.
This works if you call std::all_of() without explicit template arguments - I'm not sure why you were trying to provide them.
Reduced repro:
C:\Temp>type meow.cpp
namespace Std {
template bool AllOf(InIt, InIt, Pr) {
return true;
}
template <typename T> struct RemoveRef {
using type = T;
};
template <typename T> struct RemoveRef {
using type = T;
};
template <typename T> struct RemoveRef {
using type = T;
};
template <typename T> constexpr T&& Forward(typename RemoveRef<T>::type& t) noexcept {
return static_cast(t);
}
}
template struct Meow {
template auto operator()(Args&&... args) const
-> decltype(Std::AllOf(Std::Forward<Args>(args)...)) {
return Std::AllOf(Std::Forward<Args>(args)...);
}
};
int main() {
Meow<> alg;
alg(10, 10, 3.14);
}
C:\Temp>cl /EHsc /nologo /W4 meow.cpp
meow.cpp
meow.cpp(23): error C3546: '...': there are no parameter packs available to expand
meow.cpp(29): note: see reference to class template instantiation 'Meow<>' being compiled
C:\Temp>clang-cl /EHsc /nologo /W4 meow.cpp
C:\Temp>
Thanks,
STL
-----Original Message-----
From: Boost [mailto:boost-bounces@lists.boost.org] On Behalf Of Joaquin M López Muñoz via Boost
Sent: Friday, June 2, 2017 9:02 AM
To: boost@lists.boost.org
Cc: Joaquin M López Muñoz
Subject: [boost] [poly_collection][VS 2017] Potential compiler bug
Hi,
Boost.PolyCollection tests have started to cycle and I found VS 2017 aka MSVC 14.1 fails at test_algorithm.cpp:
https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Ftinyurl.com%2Fyb4zdkys&data=02%7C01%7Cstl%40exchange.microsoft.com%7Cf1f8085f63704a3d13f408d4a9d0d4b0%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636320161769104283&sdata=lmdoZRJng1ZpCUv9w16gOsR7UAD%2BCuIcmYeUDN8ah50%3D&reserved=0
whereas this test compiles and runs OK with VS 2015 aka MSVC 4.0 (_MSC_FULL_VER = 190023026). I've distilled down the problem to this test case:
#include <algorithm>
#include <utility>
template
struct all_of
{
template
auto operator()(Args&&... args)const->
decltype(std::all_of(std::forward<Args>(args)...))
{
return std::all_of(std::forward<Args>(args)...);
}
};
int main()
{
int x;
all_of<> alg;
alg(&x,&x,[](int){return true;});
}
which works fine with GCC and VS 2015 but fails in webcompiler.cloudapp.net with
Compiled with /EHsc /nologo /W4 /c
main.cpp
main.cpp(9): error C3546: '...': there are no parameter packs available to expand
main.cpp(18): note: see reference to class template instantiation 'all_of<>' being compiled
(_MSC_FULL_VER = 191125331, which I think is VS 2017.3 or something).
This looks like a regression to me. Deleting the ->decltype(...) bit makes the problem go away but I need to stay within C+11.
* Can someone (STL?) confirm this is indeed a compiler bug?
* Any rewording of the code that might be generally applicable to C++11 so that I don't have to include a specific workaround for VS 2017?
Thank you,
Joaquín M López Muñoz
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