bug#28329: 25.2; Eshell: 40M+ output: Stack overflow in regexp matcher

[Pierre Neidhardt]

Alright, I run into this again while emerging qtwebengine on Gentoo.
Now I think about it, this is the only and systematic cause of the issue
for me.
I suspect that emerging / compiling Chrome or affiliated projects would
also trigger the issue.

This time I managed to save the output, 60M+ big.

I tried to following

- emacs -Q
- M-x eshell
- cat portage.output.log

It took about 2 hours to complete!  While it takes half a second to
paste to the buffer.
Damn! Eshell's filters are slow! :/

That being said, no issue doing that.  So the output "saved after the
fact" does not seem to produce the issue.

-- 
Pierre Neidhardt

Finagle's Seventh Law:
        The perversity of the universe tends toward a maximum.