libio

[Roland McGrath]

> Why would argp need to be reentrant?  

Why shouldn't it be?  The only thing that makes it hard now is the use of
getopt with its globals.  A user-supplied parser function might want to do
anything, including other argp calls on other groups (e.g. perhaps you want
to parts --foo-opts="-a -b -c" and have that argp_parse on an argp
associated with "foo").

> Not using getopt just means more code for no obvious reason.

It could in fact be less code.  The argp code is rather hairy to produce
the data structures for getopt_long.