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From: Leisner.Henr@xerox.com (marty)
Newsgroups: comp.os.minix
Subject: Re: Zen and the Art of Library Programming
Message-ID: <7259@nigel.udel.EDU>
Date: 3 Jan 90 02:08:46 GMT
Sender: mmdf@udel.EDU
Lines: 60

Norbert Schlenker says: {{


----------------------------------------------------------------------------
#include <assert.h>
#include <stdio.h>

abort()
{
  while (1)
	fprintf(stderr, "Stupid jerk!\n");
}

main()
{
  assert(0==1);
}

----------------------------------------------------------------------------

This is a valid ANSI C program which should terminate with a SIGABRT
signal.
Instead, the linker will use the program's definition of abort(), and this
program will go into an infinite loop when run.  (Just as an aside, this is
a useful test program for many compilers that claim ANSI compatibility.)
}}

What is the compiler supposed to do with the program?  Generate a warning?
Generate a fatal error?  Its valid C code.  Why should the compiler (for
the language) know anything about the library functions (this ain't PL/1).

I quickly glanced through the May, 88 dpans and found nothing to confirm or
deny it.  Anyone have a reference?

While having no proof one way or another, I maintain   redefining library
functions is within the spirit of C.  I often do it since the library
version doesn't do what I want or has problems or whatever.  Recompiling
the source code with magic macros to use different functions (i.e. cc
-Dabort=myabort) is insufficient -- what if I want to library functions to
use my version ?


A common mistake by beginning C programmers is to use library functions
names for their own functions and then watch the chaos that follows (read
and write are good examples, especially when the program does STDIO) .

Part of the spirit of C I enjoy so much is the assumption the programmer
knows what he's doing (maybe he wants to redefine write() -- i.e. perhaps
do some special profiling and then generate the syscall).

One more note:
Does the Minix compiling system properly understand  public/private?  I
understood at one time static really didn't do anything regarding
name-space pollution.

marty
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