cmake -DCMAKE_CXX_STANDARD=20 failure

[jingliangliang1]

When i modify the .github/workflow cmake.yml, set -DCMAKE_CXX_STANDARD=20, in order to test systemc-3.0.0 and cci cmake with c++ standard 20.
Finally, it is failure when step configure cci.

Question: cci is not supported c++ standard 20?

[aut0]

Could you please post how to reproduce your issue, i.e. what commands did you enter, what was the output ...

[jingliangliang1]

I fork cci repo, then modify the .github/workflow/cmake.yml.
https://github.com/jingliangliang1/cci/actions/runs/11829314361/workflow , the url is i modified as requested and removed what i did not need. it is failure with c++ stantard 20, systemc 3.0.0.

https://github.com/jingliangliang1/cci/actions/runs/11829327254/workflow, this is success with c++ stantard 17 , systemc 3.0.0 .

[jingliangliang1]

In file included from /usr/include/c++/12/bits/stl_iterator_base_types.h:71,
from /usr/include/c++/12/bits/stl_algobase.h:65,
from /usr/include/c++/12/vector:60,
from /home/runner/work/cci/cci/systemc/3.0.0/include/sysc/kernel/sc_cmnhdr.h:134,
from /home/runner/work/cci/cci/systemc/3.0.0/include/systemc:70,
from /home/runner/work/cci/cci/src/cci/core/systemc.h:50,
from /home/runner/work/cci/cci/src/cci/core/cci_cmnhdr.h:32,
from /home/runner/work/cci/cci/src/cci/core/cci_value.cpp:30:
/usr/include/c++/12/bits/iterator_concepts.h: In substitution of ‘template using __iter_value_t = typename std::__detail::__iter_traits_impl<_Tp, std::indirectly_readable_traits<_Iter> >::type::value_type [with _Tp = cci::cci_value_iteratorcci::cci_value_map_elem_cref]’:
/usr/include/c++/12/bits/iterator_concepts.h:303:11: required by substitution of ‘template using iter_value_t = std::__detail::__iter_value_t<typename std::remove_cvref<_Tp>::type> [with _Tp = cci::cci_value_iteratorcci::cci_value_map_elem_cref]’
/usr/include/c++/12/bits/stl_iterator.h:169:13: required from ‘class std::reverse_iterator<cci::cci_value_iteratorcci::cci_value_map_elem_cref >’
/home/runner/work/cci/cci/src/cci/core/cci_value.h:896:5: required from here
/usr/include/c++/12/bits/iterator_concepts.h:298:13: error: no type named ‘value_type’ in ‘std::__detail::__iter_traits<cci::cci_value_iteratorcci::cci_value_map_elem_cref, std::indirectly_readable_traits<cci::cci_value_iteratorcci::cci_value_map_elem_cref > >’ {aka ‘struct std::indirectly_readable_traits<cci::cci_value_iteratorcci::cci_value_map_elem_cref >’}
298 | using __iter_value_t = typename
| ^~~~~~~~~~~~~~
/usr/include/c++/12/bits/iterator_concepts.h: In substitution of ‘template using __iter_value_t = typename std::__detail::__iter_traits_impl<_Tp, std::indirectly_readable_traits<_Iter> >::type::value_type [with _Tp = cci::cci_value_iteratorcci::cci_value_map_elem_ref]’:
/usr/include/c++/12/bits/iterator_concepts.h:303:11: required by substitution of ‘template using iter_value_t = std::__detail::__iter_value_t<typename std::remove_cvref<_Tp>::type> [with _Tp = cci::cci_value_iteratorcci::cci_value_map_elem_ref]’
/usr/include/c++/12/bits/stl_iterator.h:169:13: required from ‘class std::reverse_iterator<cci::cci_value_iteratorcci::cci_value_map_elem_ref >’
/home/runner/work/cci/cci/src/cci/core/cci_value.h:1011:5: required from here
/usr/include/c++/12/bits/iterator_concepts.h:298:13: error: no type named ‘value_type’ in ‘std::__detail::__iter_traits<cci::cci_value_iteratorcci::cci_value_map_elem_ref, std::indirectly_readable_traits<cci::cci_value_iteratorcci::cci_value_map_elem_ref > >’ {aka ‘struct std::indirectly_readable_traits<cci::cci_value_iteratorcci::cci_value_map_elem_ref >’}
gmake[2]: *** [src/CMakeFiles/cci.dir/build.make:76: src/CMakeFiles/cci.dir/cci/core/cci_value_converter.cpp.o] Error 1
gmake[2]: *** Waiting for unfinished jobs....
gmake[2]: *** [src/CMakeFiles/cci.dir/build.make:118: src/CMakeFiles/cci.dir/cci/utils/consuming_broker.cpp.o] Error 1
gmake[2]: *** [src/CMakeFiles/cci.dir/build.make:104: src/CMakeFiles/cci.dir/cci/core/cci_value.cpp.o] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:155: src/CMakeFiles/cci.dir/all] Error 2
gmake: *** [Makefile:136: all] Error 2
Error: Process completed with exit code 2.

[jingliangliang1]

I modifed the file src/cci/core/cci_value.h line no.767 and no.794.

line no.767:
replace "typedef void value_type;" by "using value_type = cci_value_map_elem_cref;"
line no.794:
replace "typedef void value_type;" by "using value_type = cci_value_map_elem_ref;"

details：
e124d71

[jingliangliang1]

I don't know what the consequences of my changes are, but the current changes do compile successfully using the C++20 standard. Please help me to confirm whether there are any other hidden dangers or not. @aut0 Thanks very much.