Missing #include's for in_place_factory when compiling for CUDA with clang

[jzmaddock]

I'm not sure if this is an optional or Boost.Format issue, but I suspect this belongs here.

The issue is that some optional methods use in_place_factory as an argument to is_base_of which absolutely requires a complete type as argument, but so far as I can see in_place_factory is only ever forward declared.

When compiling for CUDA with clang this leads to:

In file included from <source>:14:
In file included from /opt/compiler-explorer/libs/boost_1_77_0/boost/format.hpp:38:
In file included from /opt/compiler-explorer/libs/boost_1_77_0/boost/format/internals.hpp:21:
In file included from /opt/compiler-explorer/libs/boost_1_77_0/boost/optional.hpp:15:
In file included from /opt/compiler-explorer/libs/boost_1_77_0/boost/optional/optional.hpp:43:
In file included from /opt/compiler-explorer/libs/boost_1_77_0/boost/type_traits/is_base_of.hpp:12:
/opt/compiler-explorer/libs/boost_1_77_0/boost/type_traits/is_base_and_derived.hpp:142:25: error: invalid application of 'sizeof' to an incomplete type 'boost::in_place_factory_base'
    BOOST_STATIC_ASSERT(sizeof(B) != 0);
                        ^~~~~~~~~
/opt/compiler-explorer/libs/boost_1_77_0/boost/static_assert.hpp:70:55: note: expanded from macro 'BOOST_STATIC_ASSERT'
#     define BOOST_STATIC_ASSERT( ... ) static_assert(__VA_ARGS__, #__VA_ARGS__)
                                                      ^~~~~~~~~~~
/opt/compiler-explorer/libs/boost_1_77_0/boost/type_traits/is_base_and_derived.hpp:217:41: note: in instantiation of template class 'boost::detail::is_base_and_derived_impl2<boost::in_place_factory_base, std::locale>' requested here
    BOOST_STATIC_CONSTANT(bool, value = bound_type::value);
                                        ^
/opt/compiler-explorer/libs/boost_1_77_0/boost/type_traits/is_base_of.hpp:25:31: note: in instantiation of template class 'boost::detail::is_base_and_derived_impl<boost::in_place_factory_base, std::locale>' requested here
            (::boost::detail::is_base_and_derived_impl<ncvB,ncvD>::value) ||
                              ^
/opt/compiler-explorer/libs/boost_1_77_0/boost/type_traits/is_base_of.hpp:31:58: note: in instantiation of template class 'boost::detail::is_base_of_imp<boost::in_place_factory_base, std::locale>' requested here
      : public integral_constant<bool, (::boost::detail::is_base_of_imp<Base, Derived>::value)> {};
                                                         ^
/opt/compiler-explorer/libs/boost_1_77_0/boost/optional/optional.hpp:794:32: note: in instantiation of template class 'boost::is_base_of<boost::in_place_factory_base, std::locale>' requested here
  : boost::conditional< boost::is_base_of<boost::in_place_factory_base, BOOST_DEDUCED_TYPENAME boost::decay<U>::type>::value
                               ^
/opt/compiler-explorer/libs/boost_1_77_0/boost/optional/optional.hpp:823:25: note: in instantiation of template class 'boost::optional_detail::is_convertible_to_T_or_factory<std::locale, const std::locale &>' requested here
  : boost::conditional< is_convertible_to_T_or_factory<T, U>::value
                        ^
/opt/compiler-explorer/libs/boost_1_77_0/boost/core/enable_if.hpp:41:41: note: in instantiation of template class 'boost::optional_detail::is_optional_val_init_candidate<std::locale, const std::locale &, false>' requested here
  struct enable_if : public enable_if_c<Cond::value, T> {};
                                        ^
/opt/compiler-explorer/libs/boost_1_77_0/boost/optional/optional.hpp:951:53: note: in instantiation of template class 'boost::enable_if<boost::optional_detail::is_optional_val_init_candidate<std::locale, const std::locale &, false>, bool>' requested here
                      BOOST_DEDUCED_TYPENAME boost::enable_if< optional_detail::is_optional_val_init_candidate<T, Expr>, bool>::type = true
                                                    ^
/opt/compiler-explorer/libs/boost_1_77_0/boost/format/format_implementation.hpp:40:44: note: while substituting deduced template arguments into function template 'optional' [with Expr = const std::locale &]
          exceptions_(io::all_error_bits), loc_(loc)
                                           ^
/opt/compiler-explorer/libs/boost_1_77_0/boost/optional/detail/optional_factory_support.hpp:32:9: note: forward declaration of 'boost::in_place_factory_base'
  class in_place_factory_base ;

You can see the issue here: https://godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(filename:'1',fontScale:14,fontUsePx:'0',j:1,lang:cuda,selection:(endColumn:23,endLineNumber:9,positionColumn:23,positionLineNumber:9,selectionStartColumn:23,selectionStartLineNumber:9,startColumn:23,startLineNumber:9),source:'%23include+%3Cboost/config.hpp%3E%0A//%0A//+These+%23undefs+reflect+the+current+state+of+Boost.Config+develop+compared+to+1.77:%0A//%0A%23undef+BOOST_NO_CXX11_VARIADIC_TEMPLATES%0A%23undef+BOOST_NO_VARIADIC_TEMPLATES%0A//%0A//+These+includes+are+required+to+make+this+compile,%0A//+uncomment+to+remove+the+errors:%0A//%0A//%23include+%3Cboost/utility/in_place_factory.hpp%3E%0A//%23include+%3Cboost/utility/typed_in_place_factory.hpp%3E%0A%0A%23include+%3Cboost/format.hpp%3E%0A'),l:'5',n:'0',o:'CUDA+C%2B%2B+source+%231',t:'0')),k:63.22701688555347,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((g:!((h:compiler,i:(compiler:cuclang1100,filters:(b:'0',binary:'1',commentOnly:'0',demangle:'0',directives:'0',execute:'1',intel:'0',libraryCode:'0',trim:'1'),flagsViewOpen:'1',fontScale:14,fontUsePx:'0',j:1,lang:cuda,libs:!(),options:'-std%3Dc%2B%2B14+-O3+-I/opt/compiler-explorer/libs/boost_1_77_0/',selection:(endColumn:1,endLineNumber:1,positionColumn:1,positionLineNumber:1,selectionStartColumn:1,selectionStartLineNumber:1,startColumn:1,startLineNumber:1),source:1,tree:'1'),l:'5',n:'0',o:'clang+11.0.0+sm_75+CUDA-10.2+(CUDA+C%2B%2B,+Editor+%231,+Compiler+%231)',t:'0')),header:(),k:43.667751209994,l:'4',m:50,n:'0',o:'',s:0,t:'0'),(g:!((h:output,i:(compiler:1,editor:1,fontScale:12,fontUsePx:'0',wrap:'1'),l:'5',n:'0',o:'Output+of+clang+11.0.0+sm_75+CUDA-10.2+(Compiler+%231)',t:'0')),header:(),l:'4',m:50,n:'0',o:'',s:0,t:'0')),k:36.77298311444653,l:'3',n:'0',o:'',t:'0')),l:'2',m:100,n:'0',o:'',t:'0')),version:4

Adding

#include <boost/utility/in_place_factory.hpp>
#include <boost/utility/typed_in_place_factory.hpp>

Before including optional.hpp fixes the issue.

[jzmaddock]

This is moved from boostorg/config#406

[psalz]

Ah yes, I remember running into this a couple of years ago as well. The problem is not actually in Boost.Optional, but rather stems from the fact that not all Boost libraries solely rely on Boost.Config for compiler detection (i.e., some roll their own). So even with the changes in boostorg/config#297 (great to finally see some movement there!) other places still need to be updated to either check for __NVCC__ instead of __CUDACC__, or, preferably, use only macros set by Boost.Config.

In this case the problem is a check in Boost.TypeTraits' intrinsic.hpp on line 163. I suspect there are several other Boost libraries with the same problem.

[jzmaddock]

In this case the problem is a check in Boost.TypeTraits' intrinsic.hpp on line 163. I suspect there are several other Boost libraries with the same problem.

That is "a" problem, not "the" problem. I'll get to that shortly, but it is still a requirement that arguments to is_base_of are complete types even if we use an intrinsic to get the answer.

[psalz]

Heh, okay sure, apologies for the absolute statement. From my (superficial) understanding it seems like there are two separate issues at hand:

1. Clang CUDA not using the available intrinsics,
2. Incomplete types being used within the fallback implementation of BOOST_IS_BASE_OF.

I am however confused as to when the branch #if defined(BOOST_CLANG) && defined(__has_feature) && !defined(__CUDACC__) is NOT being taken (aside from the bug at hand), i.e., when the fallback mechanism was supposed to kick in. I tried compiling the above example with NVCC + Clang as a host compiler (nvcc -ccbin clang++-10), and it seems that at least during the host compilation phase, __CUDACC__ is not set, leading to the intrinsics being used.

What I can say however is that replacing the check with !defined(__NVCC__) as suggested by me above is in fact not the solution, because this then does trigger the fallback for NVCC + Clang as host, causing the incomplete type error.

[jzmaddock]

The type_traits issues are addressed here: boostorg/type_traits#162