We currently use this warning (at least on x86_64):

%s: Symbol `%s' has different size in shared object, consider re-linking\n";

This evidently does not do its job because people (including, until today, me) think it's harmless:

https://bugzilla.mozilla.org/show_bug.cgi?id=496993#c1
https://lists.fedoraproject.org/pipermail/devel/2015-September/214128.html

In reality, the symbol value is truncated to the short of both options.  This can lead to overruns as a result of an incorrect sizeof value or a missing sentinel at the end of an array.

A reworded warning message should make this clearer.  It's probably too late now to refuse to start such broken programs.