Question about cmake Tpetra detection

[bangerth]

We have the following piece of code: https://github.com/dealii/dealii/blob/master/cmake/configure/configure_20_trilinos.cmake#L230-L254 Specifically, we have this code snippet we want to compile:

          using LO       = int;
          using GO       = unsigned int;
          using GO       = ${_global_index_type};

It is, interestingly, allowed to redeclare the same type via using, but only if the right hand side is the same. It is not allowed to declare it to a different type. In other words, compiling this code snippet will only work if ${_global_index_type} is unsigned int.

Is this a mistake in our cmake scripts? Or am I just not getting what this is trying to achieve?

[drwells]

Possibly related to #13972.

[tamiko]

@bangerth The line should not be repeated - this is a refactoring mistake.

Unfortunately, we have not resolved #13972 yet, meaning this configure check will always fail for any (default configured) Trilinos version after 13.2 because the Tpetra/Kokkos backend need signed ordinals.