multiples of tty streams modules cause weirdness
If libc believes itself to be in an xpg4 process, and it a pts device is opened, libc uses push_modules to push the tty streams modules.
In cases where a process doesn't expect this, this leaves you with multiples of the streams modules, like so:
In this case, we are no longer able to get the terminal size information until modules are popped such that there is only one ptem on the stack.
Either the streams modules should not screw things if they're duplicated and stacked like this, or libc should be smart about not pushing them when they're already present. Or something.
See also #9041