X/Open and actually seems to be more common (NetBSD has it). Also use
updwtmpx() rather than directly writing to the wtmpx file, though more for
reasons of aesthetics than anything practical.
[originally from svn r5678]
_XOPEN_SOURCE. We do still need _GNU_SOURCE in order to get grantpt()
on GNU systems. This allows uxpty.c to compile on NetBSD.
[originally from svn r5675]
structure, in preparation for wanting more than one of them in a
single process. This can't be done cleanly, because the whole
business with pty_pre_init pre-allocating the pty rather assumes we
want a known number of the things before we drop privileges; so
there's a horrid hack to make pty_pre_init work on platforms that
have at most one pty instance per process, but at the same time
things ought to work sensibly with more than one per process _if_
pty_pre_init isn't required.
[originally from svn r5261]
/dev/ptyXX we can open: we must also check that we can open and use
the corresponding /dev/ttyXX, because if it's been left in the wrong
mode then we will look terribly silly when we fork and _then_
discover our pty is unusable.
[originally from svn r5257]
