I have a header that declares a constinit const array, and a cpp file that initializes it with constexpr (because I want to be able to use it in further constexpr functions in that cpp file).

This triggers -Wmissing-constinit pointed at the initializing declaration, together with a suggestion to add constinit to the declaration. However, doing so leads to a compilation error, because constexpr and constinit cannot be combined on a single declaration.

CE link.