Guidance for enforcement of minimum CXX_STANDARD_VERSION in libraries. #187
Description
The beman standard doesn't have a writeup of how to ensure the minimum C++ version in compiles. From a brief check, we're actually pretty good and consistent about NOT putting this into cmakelist.txt files. But I'd like to burn that approach into the standard and remove checking from cmake if we have it anywhere. The rationale is simply that especially for header only someone might lift out the header and use it outside of our cmake -- so enforcement must be done at the C++ code level. If a library wants to check and give a nice error message, I believe this is how it should be done:
So my proposal here will be to 1) update the standard, 2) update exemplar with an example.
Before making this change I'd like to get consensus of course. @nickelpro @ednolan @inbal2l @camio thoughts?