bug#10126: M-x grep gets more and more lost further and further into the file

[jidanni]

$ cd /tmp
$ perl -wle 'print $_ x 222 for 1..33' > 4
$ emacs -nw -Q .
("grep -nH -e 3333 4")
C-x ` ...
(what-line)

Even worse is
$ seq 333 > /tmp/3
(grep "grep -nH -e 3 3")
After a few C-x ` it just gets stuck at line 28!