shad uses operator== instead of Equal

[NanmiaoWu]

• The issue is: shad should use HandleTrait::Equal, but it uses operator==.
• The detailed error info is shown as follow:

(base) nanmiao@jiujiu:~/Documents/my_project/src/SHAD/build_hpx_Debug$ make -j 10
[  2%] Built target cpp_simple_runtime
[  5%] Built target runtime
Scanning dependencies of target util
Scanning dependencies of target ei-sssp
Scanning dependencies of target shadtest_main
Scanning dependencies of target page-rank
Scanning dependencies of target pi
Scanning dependencies of target triangle-count
Scanning dependencies of target ei-triangle-count
Scanning dependencies of target ei-page-rank
Scanning dependencies of target ei-vertex_nomination
Scanning dependencies of target blackscholes
[  7%] Building CXX object src/util/CMakeFiles/util.dir/shad.cc.o
[  8%] Building CXX object examples/edge_index_graph/CMakeFiles/ei-sssp.dir/ei-sssp.cc.o
[ 10%] Building CXX object examples/array/CMakeFiles/page-rank.dir/page-rank.cc.o
[ 11%] Building CXX object examples/edge_index_graph/CMakeFiles/ei-page-rank.dir/ei-page-rank.cc.o
[ 13%] Building CXX object examples/edge_index_graph/CMakeFiles/ei-triangle-count.dir/ei-triangle-count.cc.o
[ 14%] Building CXX object examples/blackscholes/CMakeFiles/blackscholes.dir/blackscholes.cc.o
[ 16%] Building CXX object test/unit_tests/CMakeFiles/shadtest_main.dir/gtest_main.cc.o
[ 17%] Building CXX object examples/pi/CMakeFiles/pi.dir/pi.cc.o
[ 19%] Building CXX object examples/array/CMakeFiles/triangle-count.dir/triangle-count.cc.o
[ 20%] Building CXX object examples/edge_index_graph/CMakeFiles/ei-vertex_nomination.dir/ei-vertex_nomination.cc.o
In file included from /home/nanmiao/Documents/my_project/src/SHAD/include/shad/runtime/runtime.h:42,
                 from /home/nanmiao/Documents/my_project/src/SHAD/include/shad/data_structures/object_identifier.h:30,
                 from /home/nanmiao/Documents/my_project/src/SHAD/include/shad/data_structures/abstract_data_structure.h:35,
                 from /home/nanmiao/Documents/my_project/src/SHAD/include/shad/core/array.h:30,
                 from /home/nanmiao/Documents/my_project/src/SHAD/examples/pi/pi.cc:29:
/home/nanmiao/Documents/my_project/src/SHAD/include/shad/runtime/handle.h: In member function ‘bool shad::rt::Handle::IsNull() const’:
/home/nanmiao/Documents/my_project/src/SHAD/include/shad/runtime/handle.h:90:16: error: no match for ‘operator==’ (operand types are ‘const HandleTy’ {aka ‘const hpx::lcos::shared_future<void>’} and ‘shad::rt::impl::HandleTrait<shad::rt::impl::hpx_tag>::HandleTy’ {aka ‘hpx::lcos::shared_future<void>’})
   90 |     return id_ == impl::HandleTrait<TargetSystemTag>::NullValue();
      |            ~~~ ^~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |            |                                                   |
      |            shared_future<[...]>                                shared_future<[...]>

• The issue happens when I update HandleTrait in hpx_traits_mapping as follow

template <>
struct HandleTrait<hpx_tag> {
  using HandleTy = hpx::shared_future<void>;
  using ParameterTy = hpx::shared_future<void> &;
  using ConstParameterTy = const hpx::shared_future<void> &;

  static void Init(ParameterTy H, ConstParameterTy V) {
    H = V.then([](HandleTy&&){});
  }

  static HandleTy NullValue() { return hpx::shared_future<void>(); }

  static bool Equal(ConstParameterTy lhs, ConstParameterTy rhs) {
    return toUnsignedInt(lhs) == toUnsignedInt(rhs);
  }

  static std::string toString(ConstParameterTy H) {
    return std::to_string(toUnsignedInt(H));
  }

  static uint64_t toUnsignedInt(ConstParameterTy H) {
    return reinterpret_cast<uint64_t>(hpx::traits::detail::get_shared_state(H).get());
  }

  static HandleTy CreateNewHandle() { return hpx::shared_future<void>(); }

  static void WaitFor(ParameterTy H) { if (H.valid()) H.get(); }
};

[NanmiaoWu]

A workaround to this issue is: change IsNull() as follows:

  bool IsNull() const {
      return impl::HandleTrait<TargetSystemTag>::Equal(id_, impl::HandleTrait<TargetSystemTag>::NullValue());
  }