[PATCH] D103571: [flang] Support known constant lengths in DynamicType

[Valentin Clement via Phabricator via llvm-commits]

clementval added a comment.

In D103571#2832896 <https://reviews.llvm.org/D103571#2832896>, @mstorsjo wrote:

> FYI, this change broke compiling flang with GCC 7 on Ubuntu 18.04, with build errors like these:
>
>   In file included from /home/ubuntu/code/llvm-project/flang/include/flang/Evaluate/call.h:12:0,
>                    from /home/ubuntu/code/llvm-project/flang/include/flang/Evaluate/intrinsics.h:12,
>                    from /home/ubuntu/code/llvm-project/flang/lib/Evaluate/intrinsics.cpp:9:
>   /home/ubuntu/code/llvm-project/flang/include/flang/Evaluate/common.h:187:16: error: explicitly defaulted function ‘constexpr Fortran::evaluate::DynamicType& Fortran::evaluate::DynamicType::operator=(const Fortran::evaluate::DynamicType&)’ cannot be declared as constexpr because the implicit declaration is not constexpr:
>      constexpr t &operator=(const t &) = default; \
>                   ^
>   /home/ubuntu/code/llvm-project/flang/include/flang/Evaluate/type.h:103:3: note: in expansion of macro ‘CONSTEXPR_CONSTRUCTORS_AND_ASSIGNMENTS’
>      CONSTEXPR_CONSTRUCTORS_AND_ASSIGNMENTS(DynamicType)
>      ^
>   In file included from /usr/include/c++/7/bits/node_handle.h:39:0,
>                    from /usr/include/c++/7/bits/hashtable.h:37,
>                    from /usr/include/c++/7/unordered_map:47,
>                    from /usr/include/c++/7/functional:60,
>                    from /home/ubuntu/code/llvm-project/flang/include/flang/Common/idioms.h:27,
>                    from /home/ubuntu/code/llvm-project/flang/include/flang/Common/Fortran.h:15,
>                    from /home/ubuntu/code/llvm-project/flang/include/flang/Evaluate/common.h:12,
>                    from /home/ubuntu/code/llvm-project/flang/include/flang/Evaluate/call.h:12,
>                    from /home/ubuntu/code/llvm-project/flang/include/flang/Evaluate/intrinsics.h:12,
>                    from /home/ubuntu/code/llvm-project/flang/lib/Evaluate/intrinsics.cpp:9:
>   /usr/include/c++/7/optional:453:11: note: defaulted constructor calls non-constexpr ‘std::optional<long int>& std::optional<long int>::operator=(const std::optional<long int>&)’
>        class optional
>              ^~~~~~~~
>   /usr/include/c++/7/optional:453:11: note: ‘std::optional<long int>& std::optional<long int>::operator=(const std::optional<long int>&)’ is not usable as a constexpr function because:
>   /usr/include/c++/7/optional:351:7: note: defaulted constructor calls non-constexpr ‘std::_Optional_base<_Tp>& std::_Optional_base<_Tp>::operator=(const std::_Optional_base<_Tp>&) [with _Tp = long int]’
>          operator=(const _Optional_base& __other)
>          ^~~~~~~~

I have seen similar failure with GCC 7.4


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