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Date: Sat, 9 Nov 2013 12:38:42 -0500
From: Rich Felker <>
Subject: Re: request: increase TTY_NAME_MAX in limits.h

On Sat, Nov 09, 2013 at 05:20:35PM +0000, Laurent Bercot wrote:
> >If we change it I think we might as well go with the glibc value of 32
> >rather than just increasing it by 4.
>  That would be great, thanks :)
>  I'm honestly surprised that those buffers are so small, even in glibc.
> Sure, it takes up static space, and in practice a small value works for
> most people since it will usually be /dev/something, but since ttyname()
> is not supposed to ever fail with ERANGE or any kind of overflow, I was
> expecting the buffer to be PATH_MAX bytes. Or even dynamically (re)allocated -
> which would pull in malloc(), but text space + a bit of heap space is cheaper
> than static space.

I'm not sure exactly what glibc does; technically, there's no reason
the size of this internal buffer needs to match TTY_NAME_MAX. I just
chose that as a natural size for it. On most systems, where the
ttyname is /dev/xxxxx or /dev/pts/xxxxx, 20 should be sufficient and
32 should leave plenty room. Your situation is a bit odd but there's
no sense in gratuitously breaking it.


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