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From: levy@ttrdc.UUCP (Daniel R. Levy)
Newsgroups: net.lang,net.lang.c
Subject: Re: structured assembler (BASIC)  [Really: C builtin functions?]
Message-ID: <824@ttrdc.UUCP>
Date: Sat, 5-Apr-86 17:11:39 EST
Article-I.D.: ttrdc.824
Posted: Sat Apr  5 17:11:39 1986
Date-Received: Tue, 8-Apr-86 05:40:48 EST
References: <443@3comvax.UUCP> <7900003@ztivax.UUCP>
Organization: AT&T, Computer Systems Division, Skokie, IL
Lines: 43
Keywords: BASIC, C
Xref: watmath net.lang:2311 net.lang.c:8422

In article <41@cbmvax.cbmvax.cbm.UUCP>, daveh@cbmvax.UUCP writes:
>C, LISP, Pascal, BASIC, etc., all have standard built-in functions.

C has standard built-in functions????

Gee, that's a new one on me.  EVERY function called from C is an external func-
tion, or at least it was when C began.  This includes things like write(),
read(), printf(), math functions, etc.  There's no such thing as, for example,
a C builtin equivalent to the FORTRAN MAX() or the Basic INPUT which does the
right thing no what the arguments' types are, or where the returned result is
stored.  Of course, C has developed a number of "understood" conventions, like
the omnipresence of the write() and read() functions and their calling conven-
tions but they are not necessarily gospel.  That is, you could compile a
function which takes the place of read() and link it in:

read()
{
	/* This presumes that write() will remain the "standard" version! */
	write(2,"Go fly a kite, I don't feel like reading\n",41);
	return 0;
}

and sure 'nuff it would get called, at least in a Unix environment, every time
that a program tried to read something through read() or through stdio.  (I
tried it.)  Try that with any of the Basic builtins!

I do grant that these conventions like read() and write() have become, through
hallowed usage (mostly in Unix) standard enough that some C compilers can get
away with treating them as builtins without breaking any code except that which
tries to redefine these conventions.  VAX/VMS C, for instance, will treat a
call of read() as a call of something like C$$READ() while not changing a call
of reed() to a call of C$$REED() in analogy.  But that is just cosmetic stuff;
C in essence still behaves as if all functions (following macro expansions)
were external functions, so that (maybe because?) implementations which treat
them that way (e.g., Unix) are still quite valid.
-- 
 -------------------------------    Disclaimer:  The views contained herein are
|       dan levy | yvel nad      |  my own and are not at all those of my em-
|         an engihacker @        |  ployer or the administrator of any computer
| at&t computer systems division |  upon which I may hack.
|        skokie, illinois        |
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