Re: OT: Language War (Re: "C" Manual)

[Richard Cobbe <cobbe@airmail.net>]

Lo, on Tuesday, January 1, Ben Collins did write:

> On Mon, Dec 31, 2001 at 09:15:26PM -0600, Richard Cobbe wrote:
> 
> > Consider the following:
> > 
> >     char *a, *b;
> > 
> >     a = strdup("This is a sample string");
> >     b = a;
> > 
> >     free(a);
> > 
> >     /* Much code follows here, none of which modifies b. */
> > 
> >     printf("%s\n", b);
> 
> Uh, for one, this wont segfault.

Perhaps, perhaps not.  That's the thing about C---the behavior in this
case is completely undefined.  Since printf is looking for a byte with a
value of zero, if it doesn't find such a byte before it walks off the
end of the process's allocated memory, it will segfault.

> Secondly, you can make this mistake with any language that allows
> references (perl, python, and java all allow it). Just replace free()
> with some other assignment that changes what a is, and ultimately you
> change b, which referenced it, unintentionally.

True.  That, however, is not a type error of the sort that I'm
describing.  And, in any case, the behavior of the program in that
situation is well-defined by the language specification.  This is *not*
the case with C or C++.

Richard