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From: weaver@prls.UUCP
Newsgroups: comp.os.vms
Subject: Re: Why no system() under VAX C (Really why library dependance)
Message-ID: <4382@prls.UUCP>
Date: Thu, 18-Jun-87 17:31:57 EDT
Article-I.D.: prls.4382
Posted: Thu Jun 18 17:31:57 1987
Date-Received: Sat, 20-Jun-87 01:17:24 EDT
References: <8706180833.AA11384@ucbvax.Berkeley.EDU>
Reply-To: weaver@prls.UUCP (Michael Gordon Weaver)
Distribution: world
Organization: Signetics Microprocessor Division
Lines: 35

With most of the VMS languages, the libraries are distributed with the 
operating system. This was not done with VMS C at first, probably because 
of the number of fixes required on a new product.

The disadvantages I see in this is that if a change in a compiler requires a
change in the libraries, then a release of the compiler may have to wait
for a release of the operating system, and that now the programmer has to
think more about the difference between the library calls and the compiler. 
It sounds like a bug was found too near the release date to hold up VMS.

The advantage is that changes in the operating system which require changes
in the libraries cause no problem with release dates. My feeling is that 
there is more dependancies between the libraries and the operating system
than between the libraries and the compilers, so fewer problems come up 
doing things this way.

Another reason for tying the libraries to the operating system is to allow
more sharing of the code. The libraries for various languages can be combined
into shared segments for efficiency, and more of the routines called from
the library routines can be shared among the languages. 

If shared segments were distributed with the language updates, users who do 
not pay for the compilers but receive binaries (e.g. application programs from 
third parties) would have to get new shared segments every time they got a 
new binary created by a different version of the compiler.

Also, the shared segments would have to be parted out by language, or there 
would be even more trouble synchronizing releases.


-- 
Michael Gordon Weaver                   Usenet: ...pyramid!prls!weaver
Signetics Microprocessor Division
811 East Arques Avenue
Sunnyvale, California USA 94088-3409            Phone: (408) 991-3450