Silence spurious compiler warnings

[seunghwak]

We see compiler warnings basically saying some internal data member in std::optional may be used uninitialized. This lengthy warnings are very annoying and can hide important warnings/errors.

Seeing https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635, it seems like this warning is not valid and due to the fact that the compiler cannot perfectly track when an std::optional object is valid or not in every code path.

Anyways, this PR tweaks the code to silence the warnings. There is very little practical difference between the old and new code, but I don't see the annoying warnings anymore with this update.

See the below for the actual warnings.

[1/1] Building CUDA object CMakeFiles/cugraph.dir/src/structure/graph_view_mg.cu.o
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<GraphViewType, T>::edge_src_property_t(const raft::handle_t&, const GraphViewType&) [with GraphViewType = cugraph::graph_view_t<int, int, true, true>; T = int]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:425:13,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '((const std::size_t*)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::keys_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::_M_payload.std::_Optional_payload<raft::span<const int, true, 18446744073709551615>, true, true, true>::<unnamed>.std::_Optional_payload_base<raft::span<const int, true, 18446744073709551615> >::_M_payload)))[1]' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<GraphViewType, T>::edge_src_property_t(const raft::handle_t&, const GraphViewType&) [with GraphViewType = cugraph::graph_view_t<int, int, true, true>; T = int]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:425:13,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(long unsigned int*)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_size_.std::optional<long unsigned int>::<unnamed>.std::_Optional_base<long unsigned int, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>& cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>::operator=(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:375:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(const int**)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::keys_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>& cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>::operator=(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:375:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(const int**)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_start_offsets_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>& cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>::operator=(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:375:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '((std::size_t*)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_start_offsets_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::_M_payload.std::_Optional_payload<raft::span<const int, true, 18446744073709551615>, true, true, true>::<unnamed>.std::_Optional_payload_base<raft::span<const int, true, 18446744073709551615> >::_M_payload)))[1]' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<GraphViewType, T>::edge_dst_property_t(const raft::handle_t&, const GraphViewType&) [with GraphViewType = cugraph::graph_view_t<int, int, false, true>; T = int]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:527:13,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '((const std::size_t*)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::keys_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::_M_payload.std::_Optional_payload<raft::span<const int, true, 18446744073709551615>, true, true, true>::<unnamed>.std::_Optional_payload_base<raft::span<const int, true, 18446744073709551615> >::_M_payload)))[1]' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<GraphViewType, T>::edge_dst_property_t(const raft::handle_t&, const GraphViewType&) [with GraphViewType = cugraph::graph_view_t<int, int, false, true>; T = int]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:527:13,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(long unsigned int*)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_size_.std::optional<long unsigned int>::<unnamed>.std::_Optional_base<long unsigned int, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>& cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>::operator=(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:467:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(const int**)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::keys_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>& cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>::operator=(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:467:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(const int**)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_start_offsets_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>& cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>::operator=(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:467:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '((std::size_t*)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_start_offsets_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::_M_payload.std::_Optional_payload<raft::span<const int, true, 18446744073709551615>, true, true, true>::<unnamed>.std::_Optional_payload_base<raft::span<const int, true, 18446744073709551615> >::_M_payload)))[1]' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[ChuckHastings]

Would an explicit std::optional<minor_tmp_buffer_type> defined here and initialized to std::nullopt also work? That's a code pattern we use quite a bit. Would that perhaps be a closer idiom to [[maybe_unused]] until the warning issue is corrected in the compiler?

Approving either way, just wondering.

[seunghwak]

It may work as well but std::optional is for run-time resolution. Here whether minor_tmp_buffer is used or not can be determined in compile-time.

[seunghwak]

Yeah... but your comment reminded me that I didn't add [[maybe_unused]] in this update. Adding this to minor_tmp_buffer declaration.

[naimnv]

This pattern is also nice that it doesn't require if/else block.

[ChuckHastings]

/merge