I've noticed we claim in cxx-status.html that we implement P1042R1,
but it seems we don't implement any of the changes from there.
The following patch implements just the change that __VA_OPT__ determines
whether to expand to nothing or the enclosed tokens no longer based on
whether there were any tokens passed to __VA_ARGS__, but whether __VA_ARGS__
expands to any tokens (from testing apparently it has to be non-CPP_PADDING
tokens).
I'm afraid I'm completely lost about the padding preservation/removal
changes that are also in the paper, so haven't touched that part.
2020-02-14 Jakub Jelinek <jakub@redhat.com>
Partially implement P1042R1: __VA_OPT__ wording clarifications
PR preprocessor/92319
* macro.c (expand_arg): Move declarations before vaopt_state
definition.
(class vaopt_state): Move enum update_type definition earlier. Remove
m_allowed member, add m_arg and m_update members.
(vaopt_state::vaopt_state): Change last argument from bool any_args
to macro_arg *arg, initialize m_arg and m_update instead of m_allowed.
(vaopt_state::update): When bumping m_state from 1 to 2 and m_update
is ERROR, determine if __VA_ARGS__ expansion has any non-CPP_PADDING
tokens and set m_update to INCLUDE if it has any, DROP otherwise.
Return m_update instead of m_allowed ? INCLUDE : DROP in m_state >= 2.
(replace_args, create_iso_definition): Adjust last argument to
vaopt_state ctor.
* c-c++-common/cpp/va-opt-4.c: New test.
