Issue was reported privately by Philippe Makowski.
During build such error happens:
../temp/boot/jrd/scl.cpp:252:17: error: cannot pass objects of non-trivially-copyable type 'const class Firebird::MetaName' through '...'
Must say that wise compiler noticed a real bug in our code. It stayed unnoticed cause this branch is executed only in a case of corrupted ACL. But inf such case happens, this bug will cause segfault.
The issue is specific for 2.1 - previous version does not use MetaName here, next is using Arg::Str(s_class->scl_name) which handles MetaName correctly.