linux-kernel - Re: what's the purpose of MAXHOSTNAMELEN?

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Date:	Tue, 29 Dec 2009 20:28:27 +0100
From:	Samuel Thibault <samuel.thibault@...-lyon.org>
To:	"Robert P. J. Day" <rpjday@...shcourse.ca>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: what's the purpose of MAXHOSTNAMELEN?

Robert P. J. Day, le Tue 29 Dec 2009 14:19:30 -0500, a écrit :
>   so lots of people define it but no one uses it.  it *is* exported to
> user space in /usr/include/asm/param.h, but i still have no idea what
> it's for in user space.  obsolete?

It's like all these *MAX* #defines: they are a bad way to express the
system limitations.  They are bad because they end up compiled-in, but
also because people understand them as "a typical allocation length" and
get lazy.  The typical example is PATH_MAX, which is #defined to 4096.
A _lot_ of applications thus keep allocating 4KB for all paths.

See
http://www.gnu.org/software/hurd/hurd/porting/guidelines.html#PATH_MAX_tt_MAX_PATH_tt_MAXPATHL

If you could drop it (would be completely POSIX-compliant), that'd be a
great service to GNU/Hurd porters, but I bet you'll also get a lot of
angry people.

Samuel
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