input: Allow two consecutive calls to pungetc
The commit
ef91d3d6a4c39421fd3a391e02cd82f9f3aee4a8 ([PARSER]
Handle backslash newlines properly after dollar sign) created
cases where we make two consecutive calls to pungetc. As we
don't explicitly support that there are corner cases where you
end up with garbage input leading to undefined behaviour.
This patch adds explicit support for two consecutive calls to
pungetc.
Reported-by: Jilles Tjoelker <jilles@stack.nl>
Reported-by: Juergen Daubert <jue@jue.li>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>