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From: Ted Dennison <dennison@telepath.com>
Subject: Re: bitwise comparators
Date: 2000/01/18
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In article <85vr1s$9qe1@news.cis.okstate.edu>,
  dstarner98@aasaa.ofe.org wrote:
> On Mon, 17 Jan 2000 20:26:42 +0100, Alexander Van Hecke
<alexke@hotmail.com> wrote:
> >This seems like an attack on C/C++!  I'm sorry, but I have to react
on this
> >
> >> Ada has
> >> packages,
> >
> >C was ment to be used modular and for reuse : put your code in
> >separate .c and .h files.
>

Its tough to keep a straight face while reading this. You must not have
used the packging features of languages like Ada and Modula much to make
this statement. There simply is no comparison in the amount of
modularity and reusability between them.


> int mktemp() can conflict with something in another file. No use of
> header files can fix that.

A real-world example: We are using vxWorks here at work. xvWorks has no
processes, every task in the system is effectively a lightweight thread.
You can kind of think of the entire system, kernel and all, as one big
program.

We had some C code to handle reading of radio database files developed
for previous projects that we decided to reuse in our system, rather
than rewrite it in Ada (a quite sensible decision). When we took this
system out to the hardware, we had a devil of a time getting networking
to do anything. We eventually discovered that we couldn't even ping the
loopback address succesfully. That made no sense whatsoever.

After a couple of days, one of the engineers found the problem. This
completely unrelated reused C code of ours had a routine named
"checksum". Apparently, the TCP/IP stack *also* has a checksum routine,
and they are not the same.

Now a longtime C programmer would probably be indignant that neither
author used the standard idiom (aka: hack) of tacking on some kind of
namespace designator to the front of the routine's name to prevent this
kind of disasterous clash. But the engineer in you should realize that
it is silly to yell at someone for screwing up when they have been
presented with an error-prone system in the first place. Someone was
*bound* to screw up eventually.

In Ada this won't happen, because in Ada everything automaticly has its
package's namespace, and the default is *not* to export the symbol to
the system. If there is a namespace clash, the code won't compile in the
first place. So we *never* have any such trouble with our Ada routines.

--
T.E.D.

http://www.telepath.com/~dennison/Ted/TED.html


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