openpty needs a variant with a flags argument

[Eric Blake]

openpty is worthless in a multithreaded app like libvirt - there's no 
way to make the master and slave fds atomically O_CLOEXEC; libvirt would 
also like O_NONBLOCK (although atomicity on that one is not as 
important); yet not using openpty() is also painful because of the need 
for ioctl() on Solaris and HP-UX before isatty() works on the slave.  I 
know that glibc does not (yet) provide a flags variant of openpty, 
although I created a request:

http://sourceware.org/bugzilla/show_bug.cgi?id=13385

Should we go ahead and implement a safer openpty() in gnulib, while 
waiting for the glibc decision on that bug?  On Linux, it could 
atomically set FD_CLOEXEC via the use of posix_openpt(O_CLOEXEC) and 
manual build-up of the rest of the openpty() functionality; elsewhere it 
wouldn't be atomic, but would be easier to use.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org