[Dune-devel] Required CMake version

[Christian Engwer]

Dear Christoph,

Thanks for partially answering my questions :-)

I start with one further important question:

> What is dangerous, if dune-common requests 3.1 but downstream modules
> use 2.8.12. Then CMake is in the wrong mode and will interpret things
> differently. That is what we called "subtle bugs".

what happens if downstream modules impose higher requirement? Is this
also dangerous?

This is what happened before and this was one of the arguments to jump
to the newer version. Following this argument, dune-core would loose
control over which version to require.

and then to your answers

> 2) Steffen and Dominic found some bugs in older CMake version, and they
> wished to switch to CMake 3.1 already in 2015. Having the switch with
> Dune 2.6 seems reasonable.

again this is extremely vague. If we had specific cmake code, which is
necessary to work around bugs in cmake < 3.1 and is hard to maintain I
would have guessed, that someone updates this code, but this has not
happened.

As such changes didn't happen for 2.6, I think Markus question,
whether 3.1 is necessary, is totally reasonable. This does not imply
that we need to switch back to 2.8, but asking this question should
not be problem. And "we decided this" is not a proper answer.

Best
Christian