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From: mohta@necom830.cc.titech.ac.jp (Masataka Ohta)
Newsgroups: comp.unix.internals
Subject: Re: Shared libraries are not necessary
Keywords: ISC i386 shared libraries
Message-ID: <211@titccy.cc.titech.ac.jp>
Date: 20 May 91 09:43:52 GMT
References: <196@titccy.cc.titech.ac.jp> <1991May16.135009@wsl.dec.com> <202@titccy.cc.titech.ac.jp> <1991May17.075555.29787@Think.COM>
Sender: news@titccy.cc.titech.ac.jp
Organization: Tokyo Institute of Technology
Lines: 45

In article <1991May17.075555.29787@Think.COM> barmar@think.com writes:

>>Those who support shared libraries claimed it is good for software upgrade.
>>I disagreed. Usual software upgrade is not so simple. As THEIR (not mine)
>>example was introduction of DNS, I proved they are wrong.

>There are two kinds of software upgrades: those which change the interface
>to the library, and those which only change the implementation.

>Most of the common shared library designs only make the second kind simple.
>That's certainly better than nothing.

And, my claim is that the second kind is almost nothing.

Your (those who support shared libraries) example of DNS prove that.

Most software upgrade is a little more complex than can be processed by
mere library change.

>I believe they also enhanced
>the /etc/hosts version of the routine to return multiple addresses (our
>/etc/hosts file has several host names with multiple addresses).

You believe what? No. They didn't do so.

You should not have said what you believe. Instead, see
lib/libc/net/hosttable/gethostnamadr.c of 4.3BSD source. There is only
one IP address entry provided for gethostbyname().

As you don't know enough about host name look up and accompanied complexities
of its management, don't say:

>Note that an upgrade to use the DNS didn't *have* to include support for
>multiple addresses.

unless you want to be dishonest.

>In Multics, library design guidelines also make the first kind easy.  Most
>library routines with non-trivial parameters take most of the parameters as
>a pointer to a structure.  By convention, the first member of the structure
>is a version number or version string

The only parameter for gethostbyname() is, trivially, a string.

						Masataka Ohta