Fixtype of structure declarations [C:6.7.2.1] [C:A.2.2].
This is a tagged union type, introduced by fty::deftagsum.
This corresponds to struct-declaration in the grammar of [C]. Despite its name in the grammar and in this fixtype, this applies to both structures and unions; in fact, it is not a declaration of a structure, but instead it is a declaration of a member of a structure or union. So something like member-declaration would be a better name for this grammar nonterminal, but our fixtype name reflects the current grammar.
As a GCC extension, we include the possibility that
a member declaration starts with
the
As a GCC extension, we include a possibly empty list of attribute specifiers, which come after the declarator (cf. the grammar).
As explained in our ABNF grammar, we also include an empty external declaration, which syntactically consists of a semicolon.