Re: HOST_NAME_MAX

[Simon Josefsson]

Bruno Haible <address@hidden> writes:

> Simon Josefsson wrote:
>> Then I'm less sure that it makes sense for
>> gnulib's limit.h to define HOST_NAME_MAX -- programs written against
>> POSIX should not assume that symbol exists.
>
> On the other hand, the support of POSIX for unspecified maximum host
> name lengths is weak: You see in [1] that
>   - when the host name is longer than namelen, the string is truncated,
>     possibly NUL terminated or not,
>   - when gethostname fails, it is unspecified whether it sets errno.
> The reality (see lib/xgethostname.c) is even worse:
>   - when the host name is longer than namelen, then some platforms
>     return -1, others don't; some platforms even write past the specified
>     namelength bytes,
>   - the errnos appearing in this case are far from standard.
>
> I think it's a favour that gnulib can do to its users, to not force
> developers to deal with these pitfalls.
>
> And don't tell me that host names longer than 256 bytes occur frequently :-)

Thanks, your arguments are compelling and useful to have archived in
case some FreeBSD people thinks we are making things worse by
re-introducing the HOST_NAME_MAX symbol that they appear to want to get
rid of.

I guess to really get rid of the symbol, improving the POSIX
specification in this area would be useful -- however it may be hard
since deployed implementations differ.

>> Do sysconf work under mingw?  Gnulib could provide a replacement if not.
>
> That would be some work, because of the many arguments that sysconf
> should support. [2]

It is a large number of symbols, but I wonder how many of them actually
are difficult to quantify.

/Simon