Implementation-DEPENDENT code (was:strcpy)

[00704a-Liber]

The reason that I do not like the proposed change (on the net, that is) to
strcpy() is because it ENCOURAGES implementation-dependent code, which, to
put it simply, is a *bad* programming paradigm.  We should be abstracting
on at least a procedural level, if not higher.  If we can do that, then
code maintenence becomes easier, integrating new code becomes easier and
programming in general becomes easier.  Programming projects these days are
simply getting too big to be able to just 'hack' together something that
works.

One of the arguments for the change is "I have some code now which relies
on the fact that strcpy() is left-to-right."  Since this code does not
conform to C as it is defined now, I don't think ANSI should say "that's
ok.  We will change the language so that your BAD code becomes GOOD code."
(BTW, I do not want to infer that the committee IS saying this; I am just
trying to make a point.)

And if this gets 'fixed' (like a cat gets fixed--no smiley), then shouldn't
all the bad programming practices get 'fixed', too.  Take the following
code segment for example:

	#include	<stdio.h>

	int main()

	{
		int i=1;
		while (i < 10)
		{
    	    		int j;
    			if (1 == i)
        			j = 2;
    			printf("%d ", j);
    			j += 2;
    		i++;
		}
	}

On every implementation of C that I tried this on, it printed out

	2 4 6 8 10 12 14 16 18

Now, a few questions about this program.  Assuming that this program is
designed to print out the even numbers from 2 to 18 inclusive, is this a
*correct* implementation of that algorithm, given the definition of C?
NO!!  Why not??  (Think about it before peeking ahead)

The reason is that j is declared inside a block, and this block is entered
and exited through each iteration of the while loop.  [Note:  if this
block was not entered and exited through each iteration, then changing
'int j;' to 'int j=2;' should not change my output.  But it does change it
to "2 2 2 2 2 2 2 2 2 ".  If you still don't believe it's a block, then put
an extra set of braces around everything from 'int j=2' until just before
but not including 'i++;'.  You still get the same results, and the points I
am about to make still hold.]  As K&R 1 says on page 198:  "... automatic
and register variables which are not initialized are guaranteed to start
off as garbage."  This means that every time through the loop, j should
start off as garbage (and I can construct a slightly different case that
would make j garbage on some implementations) and NOT (necessarily) contain
it's previous value.

Now, because I also know a little about how C is implemented, I know why I
got even numbers instead of junk.  In a nutshell, it is because the actual
space for j is never reallocated (there is a lot more to this, but this is
not the issue).  However, there is nothing within C which guarantees that
this space is not reallocated.

SO, I repeat:  is this an example of acceptable code??  NO!!
Is this type of construct in use today?  (Unfortunately) YES!!  (and not
just in old code which nobody ever looks at, either.)  Is this bad code?
YES!  Should C be 'fixed' so that this bad code becomes *good* code?  NO!!!
Fix the bad programs; don't change the language so that these bad programs
become acceptable!


Our programming languages should encourage us to use good programming
methods.  The proposed change to strcpy() discourages abstraction on a
procedural level, and having 'tightly coupled' code where it is not needed
is simply bad programming.  We should be trying to stay away from locking
into one specific way of implementation, since no one knows what
discoveries the future might hold.  Now is the time to fix up all the *bad*
C programs; after ANSI C is passed, we probably won't get another chance.
The proposed change to strcpy() will have far reaching consequences which
many people simply aren't thinking through.  [Sorry to have been so
philosophical about it, but isn't that what the argument is all about?]

-- 
 _ __			NEVIN J. LIBER	..!ihnp4!ihlpf!nevin1	(312) 510-6194
' )  )				"The secret compartment of my ring I fill
 /  / _ , __o  ____		 with an Underdog super-energy pill."
/  (_</_\/ <__/ / <_	These are solely MY opinions, not AT&T's, blah blah blah