Oops. I hadn't test enough before reporting the bug. the -w option seems to be necessary for the crash to happen.
In case I again forget something, here is an example : $ cat num 075 42 5 pppp 19 . 0 aaa 007 &&& 15 lll 9 p 75 12 $ msort -wlc n num zsh: segmentation fault msort -wlc n num -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]