intel 19.0.5 tuple compile error

[tjhei]

Intel compiler produces various errors of this kind for me

$ icpc -v
icpc version 19.0.5.281 (gcc version 9.1.0 compatibility)

when using stdcxx17 mode (It seems like tuple support is broken). Errors look like:

/opt/apps/gcc/9.1.0/include/c++/9.1.0/tuple(553): error: pack "_UElements" does not have the same number of elements as "_Elements"
            __and_<is_nothrow_assignable<_Elements&, _UElements>...>::value;
                                                     ^
          detected during instantiation of "bool std::tuple<_Elements...>::__nothrow_assignable<_UElements...>() [with _Elements=<unsigned int, unsigned int, std::string, dealii::DataComponentInterpretation::DataComponentInterpretation>, _UElements=<>]" at line 5953 of "/scratch1/02578/theister/deal-git/source/base/data_out_base.cc"

the offending code:

       new_nonscalar_data_ranges[i] =
          std::tuple<unsigned int,
                     unsigned int,
                     std::string,
                     DataComponentInterpretation::DataComponentInterpretation>(
            std::get<0>(nonscalar_data_ranges[i]),
            std::get<1>(nonscalar_data_ranges[i]),
            std::get<2>(nonscalar_data_ranges[i]),
            DataComponentInterpretation::component_is_part_of_vector);

Minimal repo with icpc -std=cxx17 test.cc:

#include <string>
#include <vector>
#include <tuple>

int main()
{
  using mytuple=std::tuple<int,int,std::string>;
  std::vector<mytuple> vec(1);

  vec[0] = std::make_tuple(1,2,"hello");
}

By switching to cxx14 mode, everything compiles cleanly. I reported the bug to intel but we might need to blacklist/test/something for this.

[bangerth]

:-( Can you at least work around this somehow?

[tjhei]

Can you at least work around this somehow?

Yes, by compiling with DEAL_II_WITH_CXX17=off.

[drwells]

We should have added a check for this, but since intel 20 compiles cleanly and no one managed to write a fix I don't think its worth going back and adding a check for this older compiler.