Having looked closer now, I'm pretty sure you should base this patch
on top of my patch: https://commitfest.postgresql.org/41/4081/
Mainly because you also need the token version of pg_role, which is
one of the things my patch adds.
> if (regexp_pgrole[0] == '+')
For these lines you'll need to check if the original token was quoted.
If it's quoted it shouldn't use the group behaviour, and instead
compare the + character as part of the literal role.
> if (is_member(roleid, regexp_pgrole +1))
> if (is_member(roleid, ++map_role))
You use these two checks to do the same, so it's best if they are
written consistently.
> if (regexp_pgrole[0] == '+')
This check can be moved before the following line and do an early
return (like I do for "all" in my patch). Since if the first character
is a + we know that it's not \1 and thus we don't have to worry about
getting the regex match.
> if ((ofs = strstr(identLine->pg_role->string, "\\1")) != NULL)