Infinite loop in Mac OS X "od -c" (and perhaps FreeBSD)

Asked Oct 02 '14 at 14:19

Active Oct 02 '14 at 14:19

Viewed 87 times

Try this on Mac OS X (don't worry, it won't crash your computer, it just spins):

printf "\314" | od -c

It seems that character 0314 somehow tricks od in its default Unicode mode (!) to look for further input, but there is none. I browsed the source a bit: http://www.opensource.apple.com/source/shell_cmds/shell_cmds-175/hexdump/conv.c

It seems like the bug is where it does goto retry; but I'm not sure. My question is: is this really where the bug is, and how would you fix it?

For bonus points, here's a command that outright crashes, due to another bug reported on the Free BSD bugs mailing list in 2006:

printf "\314\217" | od -c

This is still not fixed in Mac OS X, and apparently not in FreeBSD either, but at least it isn't an infinite loop! This one really makes me wonder, because it's not just these two characters which cause it--you can run od -c on a wide variety of large binary files and watch it crash. Do people really not use od much since 2006?

asked Oct 02 '14 at 14:19

John Zwinck

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[File a bug report with Apple?](http://bugreport.apple.com) – Paul R Oct 02 '14 at 14:24
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I tend to use `xxd` these days - it is more flexible to my mind. – Mark Setchell Oct 02 '14 at 14:29
This looks to be fixed in yosemite - I'm not seeing either the SEGV or a spin of od when I use your examples. – Anya Shenanigans Oct 02 '14 at 17:17
enough to use `od -c /dev/random` and will crash everytime ;) the infinite loop isn't common, because here are small number of (correct) files what **ends** to few characters causing the loop. – clt60 Oct 04 '14 at 08:00

Infinite loop in Mac OS X "od -c" (and perhaps FreeBSD)

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