The CMS build system runs genreflex with --fail_on_warnings since we had historically found that warnings eventually lead to problems during production.
CMS is now attempting to deploy a new feature which uses variadic templates and requires a ROOT dictionary. However, genreflex issues a warning about a problem that actually does not affect what CMS wishes to do. The problem can be reproduced via
Then issue the following command line
[this example used CMS' genreflex but should work with any that also used C++14 when compiling.
We need a suggestion or code change to get around this that does not involve disabling the use of --fail_on_warnings since that has been crucial in the past.