Problem with using pybind11 with clang++ and C++ 14

[fbartolic]

I have a file test.cc, consisting only of #include <pybind11/pybind11.h> which I tried to compile with clang++ test.cc -std=c++14 -O2 $(python3 -m pybind11 --includes) -o example$(python3-config --extension-suffix) on CentOS 7 but I'm getting the following error:

clang++ test.cc -std=c++14 -O2  $(python3 -m pybind11 --includes) -o example$(python3-config --extension-suffix)
In file included from test.cc:1:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pybind11.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/attr.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/cast.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pytypes.h:12:
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:604:12: error: no member named 'enable_if_t' in namespace 'std'; did you mean 'enable_if'?
using std::enable_if_t;
      ~~~~~^~~~~~~~~~~
           enable_if
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/type_traits:1766:12: note: 'enable_if' declared here
    struct enable_if
           ^
In file included from test.cc:1:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pybind11.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/attr.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/cast.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pytypes.h:12:
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:605:12: error: no member named 'conditional_t' in namespace 'std'; did you mean 'conditional'?
using std::conditional_t;
      ~~~~~^~~~~~~~~~~~~
           conditional
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/type_traits:1780:12: note: 'conditional' declared here
    struct conditional
           ^
In file included from test.cc:1:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pybind11.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/attr.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/cast.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pytypes.h:12:
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:606:12: error: no member named 'remove_cv_t' in namespace 'std'; did you mean 'remove_cv'?
using std::remove_cv_t;
      ~~~~~^~~~~~~~~~~
           remove_cv
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/type_traits:1345:12: note: 'remove_cv' declared here
    struct remove_cv
           ^
In file included from test.cc:1:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pybind11.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/attr.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/cast.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pytypes.h:12:
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:607:12: error: no member named 'remove_reference_t' in namespace 'std'; did you mean 'remove_reference'?
using std::remove_reference_t;
      ~~~~~^~~~~~~~~~~~~~~~~~
           remove_reference
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/type_traits:1374:12: note: 'remove_reference' declared here
    struct remove_reference
           ^
In file included from test.cc:1:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pybind11.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/attr.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/cast.h:13:
In file included from /home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/pytypes.h:12:
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:617:12: error: no member named 'index_sequence' in namespace 'std'
using std::index_sequence;
      ~~~~~^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:618:12: error: no member named 'make_index_sequence' in namespace 'std'
using std::make_index_sequence;
      ~~~~~^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:628:85: error: use of undeclared identifier 'index_sequence'
template <size_t... IPrev, size_t I, bool B, bool... Bs> struct select_indices_impl<index_sequence<IPrev...>, I, B, Bs...>
                                                                                    ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:629:44: error: use of undeclared identifier 'index_sequence'
    : select_indices_impl<conditional_t<B, index_sequence<IPrev..., I>, index_sequence<IPrev...>>, I + 1, Bs...> {};
                                           ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:629:100: error: expected class name
    : select_indices_impl<conditional_t<B, index_sequence<IPrev..., I>, index_sequence<IPrev...>>, I + 1, Bs...> {};
                                                                                                   ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:629:107: error: expected class name
    : select_indices_impl<conditional_t<B, index_sequence<IPrev..., I>, index_sequence<IPrev...>>, I + 1, Bs...> {};
                                                                                                          ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:630:75: error: use of undeclared identifier 'index_sequence'
template <bool... Bs> using select_indices = typename select_indices_impl<index_sequence<>, 0, Bs...>::type;
                                                                          ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:733:18: error: no template named 'conditional_t'; did you mean 'conditional'?
    using type = conditional_t<found, typename pack_element<index, Ts...>::type, Default>;
                 ^~~~~~~~~~~~~
                 conditional
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:605:12: note: 'conditional' declared here
using std::conditional_t;
           ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:799:43: error: no template named 'remove_reference_t'; did you mean 'remove_reference'?
template <typename Function, typename F = remove_reference_t<Function>>
                                          ^~~~~~~~~~~~~~~~~~
                                          remove_reference
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:607:12: note: 'remove_reference' declared here
using std::remove_reference_t;
           ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:800:30: error: no template named 'conditional_t'; did you mean 'conditional'?
using function_signature_t = conditional_t<
                             ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:605:12: note: 'conditional' declared here
using std::conditional_t;
           ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:803:14: error: no template named 'conditional_t'; did you mean 'conditional'?
    typename conditional_t<
             ^~~~~~~~~~~~~
             conditional
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:605:12: note: 'conditional' declared here
using std::conditional_t;
           ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:813:59: error: use of undeclared identifier 'remove_reference_t'
template <typename T> using is_lambda = satisfies_none_of<remove_reference_t<T>,
                                                          ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:873:48: error: use of undeclared identifier 'enable_if_t'
template <typename T> struct is_fmt_numeric<T, enable_if_t<std::is_arithmetic<T>::value>> {
                                               ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:873:89: error: expected unqualified-id
template <typename T> struct is_fmt_numeric<T, enable_if_t<std::is_arithmetic<T>::value>> {
                                                                                        ^
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:881:59: error: no template named 'enable_if_t' in namespace 'pybind11::detail'; did you mean 'enable_if'?
template <typename T> struct format_descriptor<T, detail::enable_if_t<std::is_arithmetic<T>::value>> {
                                                  ~~~~~~~~^~~~~~~~~~~
                                                          enable_if
/home/fb90/miniforge3/envs/caustics/lib/python3.9/site-packages/pybind11/include/pybind11/detail/common.h:604:12: note: 'enable_if' declared here
using std::enable_if_t;
           ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

This has something to with lack of support for C++14 but I don't understand the reference to my system's gcc (an old version lacking support for C++14) since I'm compiling this with clang++. Does anyone know what's going on here?

[fbartolic]

The solution was to pass the --gcc-toolchain=/path_to_newer_gcc/ to clang++. This seems to fix the problem.